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package scalatest

ScalaTest's main traits, classes, and other members, including members supporting ScalaTest's DSL for the Scala interpreter.

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  1. case class AbortedStatus(ex: Throwable) extends Status with Serializable with Product with Serializable

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  2. trait Alerter extends AnyRef

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    Trait providing an apply method to which alert messages about a running suite of tests can be reported.

    Trait providing an apply method to which alert messages about a running suite of tests can be reported.

    An Alerter is essentially used to wrap a Reporter and provide easy ways to send alert messages to that Reporter via an AlertProvided event. Alerter contains an apply method that takes a string and an optional payload object of type Any. The Alerter will forward the passed alert message string to the Reporter as the message parameter, and the optional payload object as the payload parameter, of an AlertProvided event.

    For insight into the differences between Alerter, Notifier, and Informer, see the main documentation for trait Alerting.

  3. trait Alerting extends AnyRef

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    Trait that contains the alert method, which can be used to send an alert to the reporter.

    Trait that contains the alert method, which can be used to send an alert to the reporter.

    One difference between alert and the info method of Informer is that info messages provided during a test are recorded and sent as part of test completion event, whereas alert messages are sent right away as AlertProvided messages. For long-running tests, alert allows you to send "alert notifications" to the reporter right away, so users can be made aware of potential problems being experienced by long-running tests. By contrast, info messages will only be seen by the user after the test has completed, and are more geared towards specification (such as Given/When/Then messages) than notification.

    The difference between alert and the update method of Updating is that alert is intended to be used for warnings or notifications of potential problems, whereas update is just for status updates. In string reporters for which ANSI color is enabled, update notifications are shown in green and alert notifications in yellow.

  4. trait AppendedClues extends AnyRef

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    Trait providing an implicit conversion that allows clues to be placed after a block of code.

    Trait providing an implicit conversion that allows clues to be placed after a block of code.

    You can use the withClue construct provided by Assertions, which is extended by every style trait in ScalaTest, to add extra information to reports of failed or canceled tests. The withClue from Assertions places the "clue string" at the front, both in the code and in the resulting message:

    withClue("This is a prepended clue;") {
      1 + 1 should equal (3)
    }
    

    The above expression will yield the failure message:

    This is a prepended clue; 2 did not equal 3

    If you mix in this trait, or import its members via its companion object, you can alternatively place the clue string at the end, like this:

    { 1 + 1 should equal (3) } withClue "now the clue comes after"
    

    The above expression will yield the failure message:

    2 did not equal 3 now the clue comes after

    If no space is already present, either at the beginning of the clue string or at the end of the current message, a space will be placed between the two, unless the clue string starts with one of the punctuation characters: comma (,), period (.), or semicolon (;). For example, the failure message in the above example includes an extra space inserted between 3 and now.

    By contrast this code, which has a clue string starting with comma:

    { 1 + 1 should equal (3) } withClue ", now the clue comes after"
    

    Will yield a failure message with no extra inserted space:

    2 did not equal 3, now the clue comes after

    The withClue method will only append the clue string to the detail message of exception types that mix in the ModifiableMessage trait. See the documentation for ModifiableMessage for more information.

    Note: the reason this functionality is not provided by Assertions directly, like the prepended withClue construct, is because appended clues require an implicit conversion. ScalaTest only gives you one implicit conversion by default in any test class to minimize the potential for conflicts with other implicit conversions you may be using. All other implicit conversions, including the one provided by this trait, you must explicitly invite into your code through inheritance or an import.

  5. case class Args(reporter: Reporter, stopper: Stopper = Stopper.default, filter: Filter = Filter.default, configMap: ConfigMap = ConfigMap.empty, distributor: Option[Distributor] = None, tracker: Tracker = Tracker.default, chosenStyles: Set[String] = Set.empty, runTestInNewInstance: Boolean = false, distributedTestSorter: Option[DistributedTestSorter] = None, distributedSuiteSorter: Option[DistributedSuiteSorter] = None) extends Product with Serializable

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  6. type Assertion = Succeeded.type

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    Marker trait that serves as the result type of assert, assume, and pending methods of trait Assertions, which return its only instance, the Succeeded singleton, or throw an exception that indicates a failed, canceled, or pending test.

    Marker trait that serves as the result type of assert, assume, and pending methods of trait Assertions, which return its only instance, the Succeeded singleton, or throw an exception that indicates a failed, canceled, or pending test.

  7. trait Assertions extends TripleEquals

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    Trait that contains ScalaTest's basic assertion methods.

    Trait that contains ScalaTest's basic assertion methods.

    You can use the assertions provided by this trait in any ScalaTest Suite, because Suite mixes in this trait. This trait is designed to be used independently of anything else in ScalaTest, though, so you can mix it into anything. (You can alternatively import the methods defined in this trait. For details, see the documentation for the Assertions companion object.

    In any Scala program, you can write assertions by invoking assert and passing in a Boolean expression, such as:

    val left = 2
    val right = 1
    assert(left == right)
    

    If the passed expression is true, assert will return normally. If false, Scala's assert will complete abruptly with an AssertionError. This behavior is provided by the assert method defined in object Predef, whose members are implicitly imported into every Scala source file. This Assertions trait defines another assert method that hides the one in Predef. It behaves the same, except that if false is passed it throws TestFailedException instead of AssertionError. Why? Because unlike AssertionError, TestFailedException carries information about exactly which item in the stack trace represents the line of test code that failed, which can help users more quickly find an offending line of code in a failing test.

    If you pass the previous Boolean expression, left == right to assert in a ScalaTest test, a failure will be reported that, because assert is implemented as a macro, includes reporting the left and right values.

    For example, given the same code as above but using ScalaTest assertions:

    import org.scalatest.Assertions._
    val left = 2
    val right = 1
    assert(left == right)
    

    The detail message in the thrown TestFailedException from this assert will be: "2 did not equal 1".

    ScalaTest's assert macro works by recognizing patterns in the AST of the expression passed to assert and, for a finite set of common expressions, giving an error message that an equivalent ScalaTest matcher expression would give. Here are some examples, where a is 1, b is 2, c is 3, d is 4, xs is List(a, b, c), and num is 1.0:

    assert(a == b || c >= d)
    // Error message: 1 did not equal 2, and 3 was not greater than or equal to 4
    
    assert(xs.exists(_ == 4))
    // Error message: List(1, 2, 3) did not contain 4
    
    assert("hello".startsWith("h") && "goodbye".endsWith("y"))
    // Error message: "hello" started with "h", but "goodbye" did not end with "y"
    
    assert(num.isInstanceOf[Int])
    // Error message: 1.0 was not instance of scala.Int
    
    assert(Some(2).isEmpty)
    // Error message: Some(2) was not empty
    

    For expressions that are not recognized, the macro currently prints out a string representation of the (desugared) AST and adds "was false". Here are some examples of error messages for unrecognized expressions:

    assert(None.isDefined)
    // Error message: scala.None.isDefined was false
    
    assert(xs.exists(i => i > 10))
    // Error message: xs.exists(((i: Int) => i.>(10))) was false
    

    You can augment the standard error message by providing a String as a second argument to assert, like this:

    val attempted = 2
    assert(attempted == 1, "Execution was attempted " + left + " times instead of 1 time")
    

    Using this form of assert, the failure report will be more specific to your problem domain, thereby helping you debug the problem. This Assertions trait also mixes in the TripleEquals, which gives you a === operator that allows you to customize Equality, perform equality checks with numeric Tolerance, and enforce type constraints at compile time with sibling traits TypeCheckedTripleEquals and ConversionCheckedTripleEquals.

    Expected results

    Although the assert macro provides a natural, readable extension to Scala's assert mechanism that provides good error messages, as the operands become lengthy, the code becomes less readable. In addition, the error messages generated for == and === comparisons don't distinguish between actual and expected values. The operands are just called left and right, because if one were named expected and the other actual, it would be difficult for people to remember which was which. To help with these limitations of assertions, Suite includes a method called assertResult that can be used as an alternative to assert. To use assertResult, you place the expected value in parentheses after assertResult, followed by curly braces containing code that should result in the expected value. For example:

    val a = 5
    val b = 2
    assertResult(2) {
      a - b
    }
    

    In this case, the expected value is 2, and the code being tested is a - b. This assertion will fail, and the detail message in the TestFailedException will read, "Expected 2, but got 3."

    Forcing failures

    If you just need the test to fail, you can write:

    fail()
    

    Or, if you want the test to fail with a message, write:

    fail("I've got a bad feeling about this")
    

    Intercepted exceptions

    Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. You can do this in the JUnit 3 style, like this:

    val s = "hi"
    try {
      s.charAt(-1)
      fail()
    }
    catch {
      case _: IndexOutOfBoundsException => // Expected, so continue
    }
    

    If charAt throws IndexOutOfBoundsException as expected, control will transfer to the catch case, which does nothing. If, however, charAt fails to throw an exception, the next statement, fail(), will be run. The fail method always completes abruptly with a TestFailedException, thereby signaling a failed test.

    To make this common use case easier to express and read, ScalaTest provides an intercept method. You use it like this:

    val s = "hi"
    intercept[IndexOutOfBoundsException] {
      s.charAt(-1)
    }
    

    This code behaves much like the previous example. If charAt throws an instance of IndexOutOfBoundsException, intercept will return that exception. But if charAt completes normally, or throws a different exception, intercept will complete abruptly with a TestFailedException. intercept returns the caught exception so that you can inspect it further if you wish, for example, to ensure that data contained inside the exception has the expected values.

    Checking that a snippet of code does or does not compile

    Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest's Assertions trait includes the following syntax for that purpose:

    assertDoesNotCompile("val a: String = 1")
    

    If you want to ensure that a snippet of code does not compile because of a type error (as opposed to a syntax error), use:

    assertTypeError("val a: String = 1")
    

    Note that the assertTypeError call will only succeed if the given snippet of code does not compile because of a type error. A syntax error will still result on a thrown TestFailedException.

    If you want to state that a snippet of code does compile, you can make that more obvious with:

    assertCompiles("val a: Int = 1")
    

    Although the previous three constructs are implemented with macros that determine at compile time whether the snippet of code represented by the string does or does not compile, errors are reported as test failures at runtime.

    Assumptions

    Trait Assertions also provides methods that allow you to cancel a test. You would cancel a test if a resource required by the test was unavailable. For example, if a test requires an external database to be online, and it isn't, the test could be canceled to indicate it was unable to run because of the missing database. Such a test assumes a database is available, and you can use the assume method to indicate this at the beginning of the test, like this:

    assume(database.isAvailable)
    

    For each overloaded assert method, trait Assertions provides an overloaded assume method with an identical signature and behavior, except the assume methods throw TestCanceledException whereas the assert methods throw TestFailedException. As with assert, assume hides a Scala method in Predef that performs a similar function, but throws AssertionError. And just as you can with assert, you will get an error message extracted by a macro from the AST passed to assume, and can optionally provide a clue string to augment this error message. Here are some examples:

    assume(database.isAvailable, "The database was down again")
    assume(database.getAllUsers.count === 9)
    

    Forcing cancelations

    For each overloaded fail method, there's a corresponding cancel method with an identical signature and behavior, except the cancel methods throw TestCanceledException whereas the fail methods throw TestFailedException. Thus if you just need to cancel a test, you can write:

    cancel()
    

    If you want to cancel the test with a message, just place the message in the parentheses:

    cancel("Can't run the test because no internet connection was found")
    

    Getting a clue

    If you want more information that is provided by default by the methods if this trait, you can supply a "clue" string in one of several ways. The extra information (or "clues") you provide will be included in the detail message of the thrown exception. Both assert and assertResult provide a way for a clue to be included directly, intercept does not. Here's an example of clues provided directly in assert:

    assert(1 + 1 === 3, "this is a clue")
    

    and in assertResult:

    assertResult(3, "this is a clue") { 1 + 1 }
    

    The exceptions thrown by the previous two statements will include the clue string, "this is a clue", in the exception's detail message. To get the same clue in the detail message of an exception thrown by a failed intercept call requires using withClue:

    withClue("this is a clue") {
      intercept[IndexOutOfBoundsException] {
        "hi".charAt(-1)
      }
    }
    

    The withClue method will only prepend the clue string to the detail message of exception types that mix in the ModifiableMessage trait. See the documentation for ModifiableMessage for more information. If you wish to place a clue string after a block of code, see the documentation for AppendedClues.

    Note: ScalaTest's assertTypeError construct is in part inspired by the illTyped macro of shapeless.

  8. abstract class AsyncFeatureSpec extends AsyncFeatureSpecLike

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  9. trait AsyncFeatureSpecLike extends AsyncSuite with AsyncTestRegistration

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    Implementation trait for class FeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    Implementation trait for class FeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    FeatureSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FeatureSpec into some other class, you can use this trait instead, because class FeatureSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FeatureSpec.

  10. abstract class AsyncFlatSpec extends AsyncFlatSpecLike

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  11. trait AsyncFlatSpecLike extends AsyncSuite with AsyncTestRegistration with ShouldVerb with MustVerb with CanVerb

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    Implementation trait for class FlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class FlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    FlatSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FlatSpec into some other class, you can use this trait instead, because class FlatSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FlatSpec.

  12. abstract class AsyncFreeSpec extends AsyncFreeSpecLike

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  13. trait AsyncFreeSpecLike extends AsyncSuite with AsyncTestRegistration

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    Implementation trait for class FreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    Implementation trait for class FreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    FreeSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FreeSpec into some other class, you can use this trait instead, because class FreeSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FreeSpec.

  14. abstract class AsyncFunSpec extends AsyncFunSpecLike

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  15. trait AsyncFunSpecLike extends AsyncSuite with AsyncTestRegistration

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    Implementation trait for class FunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class FunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    FunSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FunSpec into some other class, you can use this trait instead, because class FunSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FunSpec.

  16. abstract class AsyncFunSuite extends AsyncFunSuiteLike

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  17. trait AsyncFunSuiteLike extends AsyncSuite with AsyncTestRegistration

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    Implementation trait for class FunSuite, which represents a suite of tests in which each test is represented as a function value.

    Implementation trait for class FunSuite, which represents a suite of tests in which each test is represented as a function value.

    FunSuite is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FunSuite into some other class, you can use this trait instead, because class FunSuite does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FunSuite.

  18. abstract class AsyncPropSpec extends AsyncPropSpecLike

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  19. trait AsyncPropSpecLike extends AsyncSuite with AsyncTestRegistration

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    Implementation trait for class PropSpec, which represents a suite of property-based tests.

    Implementation trait for class PropSpec, which represents a suite of property-based tests.

    PropSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of PropSpec into some other class, you can use this trait instead, because class PropSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of PropSpec.

  20. trait AsyncSuite extends Suite

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  21. trait AsyncTestRegistration extends AnyRef

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    Trait for test registration support.

  22. abstract class AsyncWordSpec extends AsyncWordSpecLike

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  23. trait AsyncWordSpecLike extends AsyncSuite with AsyncTestRegistration with ShouldVerb with MustVerb with CanVerb

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    Implementation trait for class WordSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class WordSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    WordSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of WordSpec into some other class, you can use this trait instead, because class WordSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of WordSpec.

  24. trait BeforeAndAfter extends SuiteMixin

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    Trait that can be mixed into suites that need code executed before and after running each test.

    Trait that can be mixed into suites that need code executed before and after running each test.

    Recommended Usage: Use trait BeforeAndAfter when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. Note: For more insight into where BeforeAndAfter fits into the big picture, see the Shared fixtures section in the documentation for your chosen style trait.

    A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. Trait BeforeAndAfter offers one way to eliminate such code duplication: a before clause that will register code to be run before each test, and an after clause that will register code to be run after.

    Here's an example:

    package org.scalatest.examples.flatspec.beforeandafter
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FlatSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    

    The before and after methods can each only be called once per Suite, and cannot be invoked after run has been invoked. If either of the registered before or after functions complete abruptly with an exception, it will be reported as an aborted suite and no more tests will be attempted in that suite.

    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. Were you to mix ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects.

    Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead.

    The advantage this trait has over BeforeAndAfterEach is that its syntax is more concise. The main disadvantage is that it is not stackable, whereas BeforeAndAfterEach is. I.e., you can write several traits that extend BeforeAndAfterEach and provide beforeEach methods that include a call to super.beforeEach, and mix them together in various combinations. By contrast, only one call to the before registration function is allowed in a suite or spec that mixes in BeforeAndAfter. In addition, BeforeAndAfterEach allows you to access the config map and test name via the TestData passed to its beforeEach and afterEach methods, whereas BeforeAndAfter gives you no access to the config map.

  25. trait BeforeAndAfterAll extends SuiteMixin

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    Stackable trait that can be mixed into suites that need methods invoked before and after executing the suite.

    Stackable trait that can be mixed into suites that need methods invoked before and after executing the suite.

    This trait allows code to be executed before and/or after all the tests and nested suites of a suite are run. This trait overrides run and calls the beforeAll method, then calls super.run. After the super.run invocation completes, whether it returns normally or completes abruptly with an exception, this trait's run method will invoke afterAll.

    Trait BeforeAndAfterAll defines beforeAll and afterAll methods that take no parameters. This trait's implementation of these methods do nothing.

    For example, the following ExampleSpec mixes in BeforeAndAfterAll and in beforeAll, creates and writes to a temp file. Each test class, ExampleSpec and all its nested suites--OneSpec, TwoSpec, RedSpec, and BlueSpec--tests that the file exists. After all of the nested suites have executed, afterAll is invoked, which deletes the file. (Note: if you're unfamiliar with the withFixture(OneArgTest) approach to shared fixtures, check out the documentation for trait fixture.FlatSpec.)

    package org.scalatest.examples.beforeandafterall
    
    import org.scalatest._
    import java.io._
    
    trait TempFileExistsSpec extends fixture.FlatSpecLike {
    
      protected val tempFileName = "tmp.txt"
    
      type FixtureParam = File
      override def withFixture(test: OneArgTest) = {
        val file = new File(tempFileName)
        withFixture(test.toNoArgTest(file)) // loan the fixture to the test
      }
    
      "The temp file" should ("exist in " + suiteName) in { file =>
        assert(file.exists)
      }
    }
    
    class OneSpec extends TempFileExistsSpec
    class TwoSpec extends TempFileExistsSpec
    class RedSpec extends TempFileExistsSpec
    class BlueSpec extends TempFileExistsSpec
    
    class ExampleSpec extends Suites(
      new OneSpec,
      new TwoSpec,
      new RedSpec,
      new BlueSpec
    ) with TempFileExistsSpec with BeforeAndAfterAll {
    
      // Set up the temp file needed by the test, taking
      // a file name from the config map
      override def beforeAll() {
        val writer = new FileWriter(tempFileName)
        try writer.write("Hello, suite of tests!")
        finally writer.close()
      }
    
      // Delete the temp file
      override def afterAll() {
        val file = new File(tempFileName)
        file.delete()
      }
    }
    

    If you do supply a mapping for "tempFileName" in the config map, you'll see that the temp file is available to all the tests:

    scala> new ExampleSpec execute
    ExampleSpec:
    OneSpec:
    The temp file
    - should exist in OneSpec
    TwoSpec:
    The temp file
    - should exist in TwoSpec
    RedSpec:
    The temp file
    - should exist in RedSpec
    BlueSpec:
    The temp file
    - should exist in BlueSpec
    The temp file
    - should exist in ExampleSpec
    

    Note: this trait uses the Status result of Suite's "run" methods to ensure that the code in afterAll is executed after all the tests and nested suites are executed even if a Distributor is passed.

    Note that it is not guaranteed that afterAll is invoked from the same thread as beforeAll, so if there's any shared state between beforeAll and afterAll you'll need to make sure they are synchronized correctly.

  26. trait BeforeAndAfterAllConfigMap extends SuiteMixin

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    Trait that can be mixed into suites that need methods that make use of the config map invoked before and/or after executing the suite.

    Trait that can be mixed into suites that need methods that make use of the config map invoked before and/or after executing the suite.

    This trait allows code to be executed before and/or after all the tests and nested suites of a suite are run. This trait overrides run and calls the beforeAll(ConfigMap) method, then calls super.run. After the super.run invocation completes, whether it returns normally or completes abruptly with an exception, this trait's run method will invoke afterAll(ConfigMap).

    Note that this trait differs from BeforeAndAfterAll in that it gives the beforeAll and afterAll code access to the config map. If you don't need the config map, use BeforeAndAfterAll instead.

    Trait BeforeAndAfterAllConfigMap defines beforeAll and afterAll methods that take a configMap. This trait's implemention of each method does nothing.

    For example, the following ExampleSpec mixes in BeforeAndAfterAllConfigMap and in beforeAll, creates and writes to a temp file, taking the name of the temp file from the configMap. This same configMap is then passed to the run methods of the nested suites, OneSpec, TwoSpec, RedSpec, and BlueSpec, so those suites can access the filename and, therefore, the file's contents. After all of the nested suites have executed, afterAll is invoked, which again grabs the file name from the configMap and deletes the file. Each of these five test classes extend trait TempFileExistsSpec, which defines a test that ensures the temp file exists. (Note: if you're unfamiliar with the withFixture(OneArgTest) approach to shared fixtures, check out the documentation for trait fixture.FlatSpec.)

    package org.scalatest.examples.beforeandafterallconfigmap
    
    import org.scalatest._
    import java.io._
    
    trait TempFileExistsSpec extends fixture.FlatSpec {
    
      type FixtureParam = File
      override def withFixture(test: OneArgTest) = {
        val fileName = test.configMap.getRequired[String]("tempFileName")
        val file = new File(fileName)
        withFixture(test.toNoArgTest(file)) // loan the fixture to the test
      }
    
      "The temp file" should ("exist in " + suiteName) in { file =>
        assert(file.exists)
      }
    }
    
    class OneSpec extends TempFileExistsSpec
    class TwoSpec extends TempFileExistsSpec
    class RedSpec extends TempFileExistsSpec
    class BlueSpec extends TempFileExistsSpec
    
    class ExampleSpec extends Specs(
      new OneSpec,
      new TwoSpec,
      new RedSpec,
      new BlueSpec
    ) with TempFileExistsSpec with BeforeAndAfterAll {
    
      private val tempFileName = "tempFileName"
    
      // Set up the temp file needed by the test, taking
      // a file name from the config map
      override def beforeAll(cm: ConfigMap) {
        assume(
          cm.isDefinedAt(tempFileName),
          "must place a temp file name in the config map under the key: " + tempFileName
        )
        val fileName = cm.getRequired[String](tempFileName)
        val writer = new FileWriter(fileName)
        try writer.write("Hello, suite of tests!")
        finally writer.close()
      }
    
      // Delete the temp file
      override def afterAll(cm: ConfigMap) {
        val fileName = cm.getRequired[String]("tempFileName")
        val file = new File(fileName)
        file.delete()
      }
    }
    

    Running the above class in the interpreter will give an error if you don't supply a mapping for "tempFileName" in the config map:

    scala> new ExampleSpec execute
    ExampleSpec:
    Exception encountered when invoking run on a suite. *** ABORTED ***
      Exception encountered when invoking run on a suite. (:30)
    *** RUN ABORTED ***
      An exception or error caused a run to abort: must place a temp file name in the config map under the key: tempFileName (:30)
    

    If you do supply a mapping for "tempFileName" in the config map, you'll see that the temp file is available to all the tests:

    scala> new ExampleSpec execute (configMap = ConfigMap("tempFileName" -> "tmp.txt"))
    ExampleSpec:
    OneSpec:
    The temp file
    - should exist in OneSpec
    TwoSpec:
    The temp file
    - should exist in TwoSpec
    RedSpec:
    The temp file
    - should exist in RedSpec
    BlueSpec:
    The temp file
    - should exist in BlueSpec
    The temp file
    - should exist in ExampleSpec
    

    Note: As of 2.0.M5, this trait uses the newly added Status result of Suite's "run" methods to ensure that the code in afterAll is executed after all the tests and nested suites are executed even if a Distributor is passed.

    Note that it is not guaranteed that afterAll is invoked from the same thread as beforeAll, so if there's any shared state between beforeAll and afterAll you'll need to make sure they are synchronized correctly.

  27. trait BeforeAndAfterEach extends SuiteMixin

    Permalink

    Stackable trait that can be mixed into suites that need code executed before and/or after running each test.

    Stackable trait that can be mixed into suites that need code executed before and/or after running each test.

    Recommended Usage: Use trait BeforeAndAfterEach when you want to stack traits that perform side-effects before and/or after tests, rather than at the beginning or end of tests. Note: For more insight into where BeforeAndAfterEach fits into the big picture, see the Shared fixtures section in the documentation for your chosen style trait.

    A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code, and the slower your compile will likely be. Trait BeforeAndAfterEach offers one way to eliminate such code duplication: a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown).

    Here's an example:

    package org.scalatest.examples.flatspec.composingbeforeandaftereach
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally {
          builder.clear()
        }
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally {
          buffer.clear()
        }
      }
    }
    
    class ExampleSpec extends FlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    

    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception.

    The main advantage of BeforeAndAfterEach over BeforeAndAfter is that BeforeAndAfterEach. enables trait stacking. The main disadvantage of BeforeAndAfterEach compared to BeforeAndAfter is that BeforeAndAfterEach requires more boilerplate. If you don't need trait stacking, use BeforeAndAfter instead of BeforeAndAfterEach. If you want to make use of test data (the test name, config map, etc.) in your beforeEach or afterEach method, use trait BeforeAndAfterEachTestData instead.

  28. trait BeforeAndAfterEachTestData extends SuiteMixin

    Permalink

    Stackable trait that can be mixed into suites that need code that makes use of test data (test name, tags, config map, etc.) executed before and/or after running each test.

    Stackable trait that can be mixed into suites that need code that makes use of test data (test name, tags, config map, etc.) executed before and/or after running each test.

    Recommended Usage: Use trait BeforeAndAfterEachTestData when you want to stack traits that perform side-effects before and/or after tests, rather than at the beginning or end of tests, when you need access to any test data (such as the config map) in the before and/or after code. Note: For more insight into where BeforeAndAfterEachTestData fits into the big picture, see the Shared fixtures section in the documentation for your chosen style trait.

    A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. Trait BeforeAndAfterEachTestData offers one way to eliminate such code duplication: a beforeEach(TestData) method that will be run before each test (like JUnit's setUp), and an afterEach(TestData) method that will be run after (like JUnit's tearDown).

    Here's an example:

    package org.scalatest.examples.flatspec.composingbeforeandaftereachtestdata
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEachTestData { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach(td: TestData) {
        builder.append(td.name)
        super.beforeEach(td) // To be stackable, must call super.beforeEach(TestData)
      }
    
      override def afterEach(td: TestData) {
        try {
          super.afterEach(td) // To be stackable, must call super.afterEach(TestData)
        }
        finally {
          builder.clear()
        }
      }
    }
    
    trait Buffer extends BeforeAndAfterEachTestData { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach(td: TestData) {
        try {
          super.afterEach(td) // To be stackable, must call super.afterEach(TestData)
        }
        finally {
          buffer.clear()
        }
      }
    }
    
    class ExampleSpec extends FlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("!")
        assert(builder.toString === "Testing should be easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("!")
        assert(builder.toString === "Testing should be fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    

    To get the same ordering as withFixture, place your super.beforeEach(TestData) call at the end of each beforeEach(TestData) method, and the super.afterEach(TestData) call at the beginning of each afterEach(TestData) method, as shown in the previous example. It is a good idea to invoke super.afterEach(TestData) in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach(TestData) throws an exception.

    Besides enabling trait stacking, the other main advantage of BeforeAndAfterEachTestData over BeforeAndAfter is that BeforeAndAfterEachTestData allows you to make use of test data (such as the test name and config map) in your before and/or after code, whereas BeforeAndAfter does not.

    The main disadvantage of BeforeAndAfterEachTestData compared to BeforeAndAfter and BeforeAndAfterEach is that BeforeAndAfterEachTestData requires more boilerplate. If you don't need trait stacking or access to the test data, use BeforeAndAfter instead of BeforeAndAfterEachTestData. If you need trait stacking, but not access to the TestData, use BeforeAndAfterEach instead.

  29. trait CancelAfterFailure extends SuiteMixin

    Permalink

    Trait that when mixed into a Suite cancels any remaining tests in that Suite instance after a test fails.

    Trait that when mixed into a Suite cancels any remaining tests in that Suite instance after a test fails.

    The intended use case for this trait is if you have a suite of long-running tests that are related such that if one fails, you aren't interested in running the others, you can use this trait to simply cancel any remaining tests, so you need not wait long for them to complete.

    Note that this trait only cancels tests in the same Suite instance, because it uses a private volatile instance variable as a flag to indicate whether or not a test has failed. If you are running each test in its own instance, therefore, it would not cancel the remaining tests, because they would not see the same flag. For this reason, this trait contains a final implementation of a method defined in OneInstancePerTest, to prevent it from being mixed into any class that also mixes in OneInstancePerTest, including by mixing in ParallelTestExecution or a path traits.

  30. case class Canceled(exception: TestCanceledException) extends Exceptional with Product with Serializable

    Permalink

    Outcome for a test that was canceled, containing an exception describing the cause of the cancelation.

  31. trait Checkpoints extends AnyRef

    Permalink

    Trait providing class Checkpoint, which enables multiple assertions to be performed within a test, with any failures accumulated and reported together at the end of the test.

    Trait providing class Checkpoint, which enables multiple assertions to be performed within a test, with any failures accumulated and reported together at the end of the test.

    Because ScalaTest uses exceptions to signal failed assertions, normally execution of a test will stop as soon as the first failed assertion is encountered. Trait Checkpoints provides an option when you want to continue executing the remainder of the test body, or part of it, even if an assertion has already failed in that test.

    To use a Checkpoint (once you've mixed in or imported the members of trait Checkpoints), you first need to create one, like this:

    val cp = new Checkpoint
    

    Then give the Checkpoint assertions to execute by passing them (via a by-name parameter) to its apply method, like this:

    val (x, y) = (1, 2)
    cp { x should be < 0 }
    cp { y should be > 9 }
    

    Both of the above assertions will fail, but it won't be reported yet. The Checkpoint will execute them right away, each time its apply method is invoked. But it will catch the TestFailedExceptions and save them, only reporting them later when reportAll is invoked. Thus, at the end of the test, you must call reportAll, like this:

    cp.reportAll()
    

    This reportAll invocation will complete abruptly with a TestFailedException whose message includes the message, source file, and line number of each of the checkpointed assertions that previously failed. For example:

    1 was not less than 0 (in Checkpoint) at ExampleSpec.scala:12
    2 was not greater than 9 (in Checkpoint) at ExampleSpec.scala:13
    

    Make sure you invoke reportAll before the test completes, otherwise any failures that were detected by the Checkpoint will not be reported.

    Note that a Checkpoint will catch and record for later reporting (via reportAll) exceptions that mix in StackDepth except for TestCanceledException, TestRegistrationClosedException, NotAllowedException, and DuplicateTestNameException. If a block of code passed to a Checkpoint's apply method completes abruptly with any of the StackDepth exceptions in the previous list, or any non-StackDepth exception, that invocation of the apply method will complete abruptly with the same exception immediately. Unless you put reportAll in a finally clause and handle this case, such an unexpected exception will cause you to lose any information about assertions that failed earlier in the test and were recorded by the Checkpoint.

  32. final class CompositeStatus extends Status with Serializable

    Permalink

    Composite Status that aggregates its completion and failed states of set of other Statuses passed to its constructor.

    Composite Status that aggregates its completion and failed states of set of other Statuses passed to its constructor.

  33. class ConfigMap extends Map[String, Any] with MapLike[String, Any, ConfigMap] with Serializable

    Permalink

    A map of configuration data.

    A map of configuration data.

    A ConfigMap can be populated from the Runner command line via -D arguments. Runner passes it to many methods where you can use it to configure your test runs. For example, Runner passed the ConfigMap to:

    • the apply method of Reporters via RunStarting events
    • the run method of Suite
    • the runNestedSuites method of Suite
    • the runTests method of Suite
    • the runTest method of Suite
    • the withFixture(NoArgTest) method of Suite
    • the withFixture(OneArgTest) method of fixture.Suite
    • the beforeEach(TestData) method of BeforeAndAfterEachTestData
    • the afterEach(TestData) method of BeforeAndAfterEachTestData

    In addition to accessing the ConfigMap in overriden implementations of the above methods, you can also transform and pass along a modified ConfigMap.

    A ConfigMap maps string keys to values of any type, i.e., it is a Map[String, Any]. To get a configuration value in a variable of the actual type of that value, therefore, you'll need to perform an unsafe cast. If this cast fails, you'll get an exception, which so long as the ConfigMap is used only in tests, will result in either a failed or canceled test or aborted suite. To give such exceptions nice stack depths and error messages, and to eliminate the need for using asInstanceOf in your test code, ConfigMap provides three methods for accessing values at expected types.

    The getRequired method returns the value bound to a key cast to a specified type, or throws TestCanceledException if either the key is not bound or is bound to an incompatible type. Here's an example:

    val tempFileName: String = configMap.getRequired[String]("tempFileName")
    

    The getOptional method returns the value bound to a key cast to a specified type, wrapped in a Some, returns None if the key is not bound, or throws TestCanceledException if the key exists but is bound to an incompatible type. Here's an example:

    val tempFileName: Option[String] = configMap.getOptional[String]("tempFileName")
    

    The getWithDefault method returns the value bound to a key cast to a specified type, returns a specified default value if the key is not bound, or throws TestCanceledException if the key exists but is either not bound or is bound to an incompatible type. Here's an example:

    val tempFileName: String = configMap.getWithDefault[String]("tempFileName", "tmp.txt")
    

  34. final class ConfigMapWrapperSuite extends Suite

    Permalink

    Wrapper Suite that passes an instance of the config map to the constructor of the wrapped Suite when run is invoked.

    Wrapper Suite that passes an instance of the config map to the constructor of the wrapped Suite when run is invoked.

    Recommended Usage: Trait ConfigMapWrapperSuite is primarily intended to be used with the "path" traits, which can't use the usual approaches to accessing the config map because of the eager manner in which they run tests.

    Each time run is invoked on an instance of ConfigMapWrapperSuite, this suite will create a new instance of the suite to wrap, passing to the constructor the config map passed to run. This way, if the same ConfigMapWrapperSuite instance is run multiple times, each time with a different config map, an instance of the wrapped suite will be created for each config map. In addition to being passed to the wrapped suite's constructor, the config map passed to the ConfigMapWrapperSuite's run method will also be passed to the run method of the newly created wrapped suite instance.

    The config map is accessible inside a Suite in many ways. It is passed to run, runNestedSuites, runTests, and runTest. It is also passed to withFixture, accessible via a method on NoArgTest and OneArgTest. It is passed to an overloaded forms of the beforeEach and afterEach methods of trait BeforeAndAfterEach, as well as overloaded forms of the beforeAll and afterAll methods of trait BeforeAndAfterAll. Tests themselves can have information taken from the config map, or the entire config map, through various means. The config map may be passed into the test via a ConfigMapFixture, for example. Class ConfigMapWrapperSuite represents one more way to get at the config map inside a suite of test: ConfigMapWrapperSuite will pass the config map to the constructor of your suite class, bringing it easily into scope for tests and helper methods alike.

    Having the config map passed to the suite constructor might be more convenient in some cases, but in the case of the org.scalatest.path traits, it is necessary if a test needs information from a config map. The reason is that in a path trait, the test code is executed eagerly, before run is invoked. The results of the tests are registered when the tests are executed, and those results are merely reported once run is invoked. Thus by the time run has been invoked, it is too late to get the config map to the tests, which have already been executed. Using a ConfigMapWrapperSuite solves that problem. By passing the config map to the constructor, it is available early enough for the running tests to use it. Here's an example:

    import org.scalatest._
    
    @WrapWith(classOf[ConfigMapWrapperSuite])
    class ExampleSpec(configMap: ConfigMap) extends path.FunSpec {
    
      describe("A widget database") {
        it("should contain consistent values") {
          val dbName = configMap("WidgetDbName") // Can access config map
          // ...
        }
      }
    }
    

  35. trait DiagrammedAssertions extends Assertions

    Permalink

    Sub-trait of Assertions that override assert and assume methods to include a diagram showing the values of expression in the error message when the assertion or assumption fails.

    Sub-trait of Assertions that override assert and assume methods to include a diagram showing the values of expression in the error message when the assertion or assumption fails.

    Here are some examples:

    scala> import DiagrammedAssertions._
    import DiagrammedAssertions._
    
    scala> assert(a == b || c >= d)
    org.scalatest.exceptions.TestFailedException:
    
    assert(a == b || c >= d)
           | |  | |  | |  |
           1 |  2 |  3 |  4
             |    |    false
             |    false
             false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(xs.exists(_ == 4))
    org.scalatest.exceptions.TestFailedException:
    
    assert(xs.exists(_ == 4))
           |  |
           |  false
           List(1, 2, 3)
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert("hello".startsWith("h") && "goodbye".endsWith("y"))
    org.scalatest.exceptions.TestFailedException:
    
    assert("hello".startsWith("h") && "goodbye".endsWith("y"))
           |       |          |    |  |         |        |
           "hello" true       "h"  |  "goodbye" false    "y"
                                   false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(num.isInstanceOf[Int])
    org.scalatest.exceptions.TestFailedException:
    
    assert(num.isInstanceOf[Int])
           |   |
           1.0 false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(Some(2).isEmpty)
    org.scalatest.exceptions.TestFailedException:
    
    assert(Some(2).isEmpty)
           |    |  |
           |    2  false
           Some(2)
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(None.isDefined)
    org.scalatest.exceptions.TestFailedException:
    
    assert(None.isDefined)
           |    |
           None false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(xs.exists(i => i > 10))
    org.scalatest.exceptions.TestFailedException:
    
    assert(xs.exists(i => i > 10))
           |  |
           |  false
           List(1, 2, 3)
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    

    If the expression passed to assert or assume spans more than one line, DiagrammedAssertions falls back to the default style of error message, since drawing a diagram would be difficult. Here's an example showing how DiagrammedAssertions will treat a multi-line assertion (i.e., you don't get a diagram):

    scala> assert("hello".startsWith("h") &&
         |   "goodbye".endsWith("y"))
    org.scalatest.exceptions.TestFailedException: "hello" started with "h", but "goodbye" did not end with "y"
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    

    Also, since an expression diagram essentially represents multi-line ascii art, if a clue string is provided, it appears above the diagram, not after it. It will often also show up in the diagram:

    scala> assert(None.isDefined, "Don't do this at home")
    org.scalatest.exceptions.TestFailedException: Don't do this at home
    
    assert(None.isDefined, "Don't do this at home")
           |    |
           None false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    
    scala> assert(None.isDefined,
         |   "Don't do this at home")
    org.scalatest.exceptions.TestFailedException: Don't do this at home
    
    assert(None.isDefined,
           |    |
           None false
    
            at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:422)
            ...
    

    Trait DiagrammedAssertions was inspired by Peter Niederwieser's work in Spock and Expecty.

  36. trait DiagrammedExpr[T] extends AnyRef

    Permalink

    A trait that represent an expression recorded by DiagrammedExprMacro, which includes the following members:

    A trait that represent an expression recorded by DiagrammedExprMacro, which includes the following members:

    • a boolean value
    • an anchor that records the position of this expression
    • anchor values of this expression (including sub-expressions)

    DiagrammedExpr is used by code generated from DiagrammedAssertionsMacro, it needs to be public so that the generated code can be compiled. It is expected that ScalaTest users would ever need to use DiagrammedExpr directly.

  37. trait DistributedSuiteSorter extends AnyRef

    Permalink

    A sorter for the events of a run's distributed suites.

    A sorter for the events of a run's distributed suites.

    This trait is used, for example, when -PS is passed to Runner, to sort the events of distributed suites such that each suite's events are propagated together, with a timeout if an event takes too long.

  38. trait DistributedTestSorter extends AnyRef

    Permalink

    A sorter for the events of a suite's distributed tests.

    A sorter for the events of a suite's distributed tests.

    This trait is used, for example, by ParallelTestExecution to sort the events of tests back into sequential order, with a timeout if an event takes too long.

  39. trait Distributor extends AnyRef

    Permalink

    Trait whose instances facilitate parallel execution of Suites.

    Trait whose instances facilitate parallel execution of Suites. An optional Distributor is passed to the run method of Suite. If a Distributor is indeed passed, trait Suite's implementation of run will populate that Distributor with its nested Suites (by passing them to the Distributor's apply method) rather than executing the nested Suites directly. It is then up to another thread or process to execute those Suites.

    If you have a set of nested Suites that must be executed sequentially, you can mix in trait SequentialNestedSuiteExecution, which overrides runNestedSuites and calls super's runNestedSuites implementation, passing in None for the Distributor.

    Implementations of this trait must be thread safe.

  40. trait DoNotDiscover extends Annotation

    Permalink

    Annotation used to indicate that an otherwise discoverable test class should not be discovered.

    Annotation used to indicate that an otherwise discoverable test class should not be discovered.

    Note: This is actually an annotation defined in Java, not a Scala trait. It must be defined in Java instead of Scala so it will be accessible at runtime. It has been inserted into Scaladoc by pretending it is a trait.

    ScalaTest will discover any class that either extends Suite and has a public, no-arg constructor, or is annotated with a valid WrapWith annotation. If you wish to prevent a class from being discovered, simply annotate it with DoNotDiscover, like this:

    import org.scalatest._
    
    @DoNotDiscover
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    ScalaTest will run classes annotated with DoNotDiscover if asked to explicitly, it just won't discover them.

  41. trait Documenter extends (String) ⇒ Unit

    Permalink

    Trait to which markup text tests can be reported.

    Trait to which markup text tests can be reported.

    Note: Documenter will be described in more detail in a future 2.0 milestone release. As of this release you can't see its effects yet.

  42. trait Documenting extends AnyRef

    Permalink

    Trait that contains a markup method, which can be used to send markup to the Reporter.

    Trait that contains a markup method, which can be used to send markup to the Reporter.

  43. final case class DynaTags(suiteTags: Map[String, Set[String]], testTags: Map[String, Map[String, Set[String]]]) extends Serializable with Product

    Permalink

    Dynamic tags for a run.

    Dynamic tags for a run.

    Instances of this class are passed to the Filter constructor to support running selected suites and tests via dynamic tagging. For example, dynamic tags can be used to rerun tests that failed previously, or tests selected via a wildcard from Runner or the Scala interpreter.

    suiteTags

    a map from String suite ID to a set of tags for that suite.

    testTags

    a map from String suite ID to a map, whose keys are test names and values the tags for that test.

    Exceptions thrown

    NullPointerException if either suiteTags or testTags is null

  44. trait EitherValues extends AnyRef

    Permalink

    Trait that provides an implicit conversion that adds left.value and right.value methods to Either, which will return the selected value of the Either if defined, or throw TestFailedException if not.

    Trait that provides an implicit conversion that adds left.value and right.value methods to Either, which will return the selected value of the Either if defined, or throw TestFailedException if not.

    This construct allows you to express in one statement that an Either should be left or right and that its value should meet some expectation. Here's are some examples:

    either1.right.value should be > 9
    either2.left.value should be ("Muchas problemas")
    

    Or, using assertions instead of matcher expressions:

    assert(either1.right.value > 9)
    assert(either2.left.value === "Muchas problemas")
    

    Were you to simply invoke right.get or left.get on the Either, if the Either wasn't defined as expected (e.g., it was a Left when you expected a Right), it would throw a NoSuchElementException:

    val either: Either[String, Int] = Left("Muchas problemas")
    
    either.right.get should be > 9 // either.right.get throws NoSuchElementException
    

    The NoSuchElementException would cause the test to fail, but without providing a stack depth pointing to the failing line of test code. This stack depth, provided by TestFailedException (and a few other ScalaTest exceptions), makes it quicker for users to navigate to the cause of the failure. Without EitherValues, to get a stack depth exception you would need to make two statements, like this:

    val either: Either[String, Int] = Left("Muchas problemas")
    
    either should be ('right) // throws TestFailedException
    either.right.get should be > 9
    

    The EitherValues trait allows you to state that more concisely:

    val either: Either[String, Int] = Left("Muchas problemas")
    
    either.right.value should be > 9 // either.right.value throws TestFailedException
    

  45. case class Entry[K, V](key: K, value: V) extends java.util.Map.Entry[K, V] with Product with Serializable

    Permalink

    A case class implementation of java.util.Map.Entry to make it easier to test Java Maps with ScalaTest Matchers.

    A case class implementation of java.util.Map.Entry to make it easier to test Java Maps with ScalaTest Matchers.

    In Java, java.util.Map is not a subtype of java.util.Collection, and does not actually define an element type. You can ask a Java Map for an “entry set” via the entrySet method, which will return the Map's key/value pairs wrapped in a set of java.util.Map.Entry, but a Map is not actually a collection of Entry. To make Java Maps easier to work with, however, ScalaTest matchers allows you to treat a Java Map as a collection of Entry, and defines this convenience implementation of java.util.Map.Entry. Here's how you use it:

    javaMap should contain (Entry(2, 3))
    javaMap should contain oneOf (Entry(2, 3), Entry(3, 4))
    

    key

    the key of this entry

    value

    the value of this entry

  46. sealed abstract class Exceptional extends Outcome

    Permalink

    Superclass for the two outcomes of running a test that contain an exception: Failed and Canceled.

    Superclass for the two outcomes of running a test that contain an exception: Failed and Canceled.

    This class provides a toOption method that returns a Some wrapping the contained exception, and an isExceptional field with the value true. It's companion object provides an extractor that enables patterns that match a test that either failed or canceled, as in:

    outcome match {
      case Exceptional(ex) => // handle failed or canceled case
      case _ => // handle succeeded, pending, or omitted case
    }
    

  47. case class Failed(exception: Throwable) extends Exceptional with Product with Serializable

    Permalink

    Outcome for a test that failed, containing an exception describing the cause of the failure.

    Outcome for a test that failed, containing an exception describing the cause of the failure.

    Note: the difference between this Failed class and the similarly named FailedStatus object is that an instance of this class indicates one test failed, whereas the FailedStatus object indicates either one or more tests failed and/or one or more suites aborted during a run. Both are used as the result type of Suite lifecycle methods, but Failed is a possible result of withFixture, whereas FailedStatus is a possible result of run, runNestedSuites, runTests, or runTest. In short, Failed is always just about one test, whereas FailedStatus could be about something larger: multiple tests or an entire suite.

  48. class FeatureSpec extends FeatureSpecLike

    Permalink

    A suite of tests in which each test represents one scenario of a feature.

    A suite of tests in which each test represents one scenario of a feature. FeatureSpec is intended for writing tests that are "higher level" than unit tests, for example, integration tests, functional tests, and acceptance tests. You can use FeatureSpec for unit testing if you prefer, however.

    Recommended Usage: Class FeatureSpec is primarily intended for acceptance testing, including facilitating the process of programmers working alongside non-programmers to define the acceptance requirements.

    Although not required, FeatureSpec is often used together with GivenWhenThen to express acceptance requirements in more detail. Here's an example:

    package org.scalatest.examples.featurespec
    
    import org.scalatest._
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends FeatureSpec with GivenWhenThen {
    
      info("As a TV set owner")
      info("I want to be able to turn the TV on and off")
      info("So I can watch TV when I want")
      info("And save energy when I'm not watching TV")
    
      feature("TV power button") {
        scenario("User presses power button when TV is off") {
    
          Given("a TV set that is switched off")
          val tv = new TVSet
          assert(!tv.isOn)
    
          When("the power button is pressed")
          tv.pressPowerButton()
    
          Then("the TV should switch on")
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on") {
    
          Given("a TV set that is switched on")
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
    
          When("the power button is pressed")
          tv.pressPowerButton()
    
          Then("the TV should switch off")
          assert(!tv.isOn)
        }
      }
    }
    

    Note: for more information on the calls to Given, When, and Then, see the documentation for trait GivenWhenThen and the Informers section below.

    A FeatureSpec contains feature clauses and scenarios. You define a feature clause with feature, and a scenario with scenario. Both feature and scenario are methods, defined in FeatureSpec, which will be invoked by the primary constructor of StackFeatureSpec. A feature clause describes a feature of the subject (class or other entity) you are specifying and testing. In the previous example, the subject under specification and test is a Set. The feature being specified and tested is the behavior of a Set when it is empty and head is invoked. With each scenario you provide a string (the spec text) that specifies the behavior of the subject for one scenario in which the feature may be used, and a block of code that tests that behavior. You place the spec text between the parentheses, followed by the test code between curly braces. The test code will be wrapped up as a function passed as a by-name parameter to scenario, which will register the test for later execution.

    A FeatureSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Scenarios can only be registered with the scenario method while the FeatureSpec is in its registration phase. Any attempt to register a scenario after the FeatureSpec has entered its ready phase, i.e., after run has been invoked on the FeatureSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using FeatureSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Each scenario represents one test. The name of the test is the spec text passed to the scenario method. The feature name does not appear as part of the test name. In a FeatureSpec, therefore, you must take care to ensure that each test has a unique name (in other words, that each scenario has unique spec text).

    When you run a FeatureSpec, it will send Formatters in the events it sends to the Reporter. ScalaTest's built-in reporters will report these events in such a way that the output is easy to read as an informal specification of the subject being tested. For example, were you to run TVSetSpec from within the Scala interpreter:

    scala> new TVSetSpec execute
    

    You would see:

    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is off
        Given a TV set that is switched off
        When the power button is pressed
        Then the TV should switch on
      Scenario: User presses power button when TV is on
        Given a TV set that is switched on
        When the power button is pressed
        Then the TV should switch off
    

    Or, to run just the “Feature: TV power button Scenario: User presses power button when TV is on” method, you could pass that test's name, or any unique substring of the name, such as "TV is on". Here's an example:

    scala> new TVSetSpec execute "TV is on"
    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is on
        Given a TV set that is switched on
        When the power button is pressed
        Then the TV should switch off
    

    You can also pass to execute a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation for execute (below) and the ScalaTest shell.

    The execute method invokes a run method that takes two parameters. This run method, which actually executes the suite, will usually be invoked by a test runner, such as run, tools.Runner, a build tool, or an IDE.

    Note: Trait FeatureSpec's syntax is in part inspired by Cucumber, a Ruby BDD framework.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, FeatureSpec provides registration methods that start with ignore instead of scenario. For example, to temporarily disable the test named addition, just change “scenario” into “ignore,” like this:

    package org.scalatest.examples.featurespec.ignore
    
    import org.scalatest.FeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends FeatureSpec {
    
      feature("TV power button") {
        ignore("User presses power button when TV is off") {
          val tv = new TVSet
          assert(!tv.isOn)
          tv.pressPowerButton()
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on") {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new TVSetSpec execute
    
    It will run only the second scenario and report that the first scenario was ignored:
    TVSetSpec:
    Feature: TV power button
      Scenario: User presses power button when TV is off !!! IGNORED !!!
      Scenario: User presses power button when TV is on
    
    == Informers ==

    One of the parameters to FeatureSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the default reporting done by FeatureSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a scenario to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by FeatureSpec to pass such information to the reporter. You can see this in action in the initial example of this trait's documentation.

    Documenters

    FeatureSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FlatSpec that uses markup:

    package org.scalatest.examples.featurespec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FeatureSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
         def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      feature("An element can be added to an empty mutable Set") {
        scenario("When an element is added to an empty mutable Set") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.featurespec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FeatureSpec {
    
      feature("An element can be added to an empty mutable Set") {
        scenario("When an element is added to an empty mutable Set") {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    Feature: An element can be added to an empty mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
      Scenario: When an element is added to an empty mutable Set
        info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. You can mark tests as pending in a FeatureSpec like this:
    package org.scalatest.examples.featurespec.pending
    
    import org.scalatest.FeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends FeatureSpec {
    
      feature("TV power button") {
    
        scenario("User presses power button when TV is off") (pending)
    
        scenario("User presses power button when TV is on") {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of TVSetSpec with:
    scala> new TVSetSpec execute
    
    It will run both tests, but report that When empty should have size 0 is pending. You'll see:
    TVSetSpec:
    Feature: TV power button
      Scenario: User presses power button when TV is off (pending)
      Scenario: User presses power button when TV is on
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a FeatureSpec:
    package org.scalatest.examples.featurespec.infopending
    
    import org.scalatest._
    
    class TVSet {
      private var on: Boolean = false
    
      def isOn: Boolean = on
    
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends FeatureSpec with GivenWhenThen {
    
      info("As a TV set owner")
      info("I want to be able to turn the TV on and off")
      info("So I can watch TV when I want")
      info("And save energy when I'm not watching TV")
    
      feature("TV power button") {
        scenario("User presses power button when TV is off") {
          Given("a TV that is switched off")
          When("the power button is pressed")
          Then("the TV should switch on")
          pending
        }
    
        scenario("User presses power button when TV is on") {
          Given("a TV that is switched on")
          When("the power button is pressed")
          Then("the TV should switch off")
          pending
        }
      }
    }
    
    Would yield the following output when run in the interpreter:
    scala> new TVSetSpec execute
    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is off (pending)
        Given a TV that is switched off
        When the power button is pressed
        Then the TV should switch on
      Scenario: User presses power button when TV is on (pending)
        Given a TV that is switched on
        When the power button is pressed
        Then the TV should switch off 
    
    == Tagging tests == A FeatureSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a FeatureSpec, groups of tests can optionally be included and/or excluded. To tag a FeatureSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for FeatureSpecs like this:
    package org.scalatest.examples.featurespec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place FeatureSpec tests into groups like this:
    import org.scalatest.FeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends FeatureSpec {
    
      feature("TV power button") {
        scenario("User presses power button when TV is off", SlowTest) {
          val tv = new TVSet
          assert(!tv.isOn)
          tv.pressPowerButton()
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on", SlowTest, DbTest) {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a FeatureSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.featurespec.getfixture
    
    import org.scalatest.FeatureSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FeatureSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is designed to ")
          val buffer = new ListBuffer[String]
        }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          val f = fixture
          f.builder.append("encourage clear code!")
          assert(f.builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        scenario("User needs to understand what the tests are doing") {
          val f = fixture
          f.builder.append("be easy to reason about!")
          assert(f.builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.featurespec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.FeatureSpec
    
    class ExampleSpec extends FeatureSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is designed to ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is", "designed", "to")
      }
    
      feature("Simplicity") {
        // This test needs the StringBuilder fixture
        scenario("User needs to read test code written by others") {
          new Builder {
            builder.append("encourage clear code!")
            assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          }
        }
    
        // This test needs the ListBuffer[String] fixture
        scenario("User needs to understand what the tests are doing") {
          new Buffer {
            buffer += ("be", "easy", "to", "reason", "about!")
            assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy", "to", "reason", "about!"))
          }
        }
    
        // This test needs both the StringBuilder and ListBuffer
        scenario("User needs to write tests") {
          new Builder with Buffer {
            builder.append("be easy to learn!")
            buffer += ("be", "easy", "to", "remember", "how", "to", "write!")
            assert(builder.toString === "ScalaTest is designed to be easy to learn!")
            assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy",
              "to", "remember", "how", "to", "write!"))
          }
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. That is to say, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:
    package org.scalatest.examples.featurespec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends FeatureSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      scenario("This scenario should succeed") {
        assert(1 + 1 === 2)
      }
    
      scenario("This scenario should fail") {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSpec execute
    ExampleSpec:
    Scenario: This scenario should succeed
    Scenario: This scenario should fail *** FAILED ***
      2 did not equal 3 (:115)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.featurespec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.FeatureSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends FeatureSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is designed to ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is designed to ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      feature("Simplicity") {
        // This test needs the file fixture
        scenario("User needs to read test code written by others") {
          withFile { (file, writer) =>
            writer.write("encourage clear code!")
            writer.flush()
            assert(file.length === 46)
          }
        }
        // This test needs the database fixture
        scenario("User needs to understand what the tests are doing") {
          withDatabase { db =>
            db.append("be easy to reason about!")
            assert(db.toString === "ScalaTest is designed to be easy to reason about!")
          }
        }
        // This test needs both the file and the database
        scenario("User needs to write tests") {
          withDatabase { db =>
            withFile { (file, writer) => // loan-fixture methods compose
              db.append("be easy to learn!")
              writer.write("be easy to remember how to write!")
              writer.flush()
              assert(db.toString === "ScalaTest is designed to be easy to learn!")
              assert(file.length === 58)
            }
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.FeatureSpec and overriding withFixture(OneArgTest). Each test in a fixture.FeatureSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.featurespec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.FeatureSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is designed to be ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") { f =>
          f.writer.write("encourage clear code!")
          f.writer.flush()
          assert(f.file.length === 49)
        }
    
        scenario("User needs to understand what the tests are doing") { f =>
          f.writer.write("be easy to reason about!")
          f.writer.flush()
          assert(f.file.length === 52)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.FeatureSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.featurespec.beforeandafter
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FeatureSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is designed to ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.featurespec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is designed to ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FeatureSpec with Builder with Buffer {
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
          buffer += "easy"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.featurespec.composingbeforeandaftereach
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is designed to ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FeatureSpec with Builder with Buffer {
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
          buffer += "easy"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared scenarios == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a FeatureSpec, you first place shared tests (i.e., shared scenarios) in behavior functions. These behavior functions will be invoked during the construction phase of any FeatureSpec that uses them, so that the scenarios they contain will be registered as scenarios in that FeatureSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several scenarios that make sense any time the stack is non-empty. Thus you'd ideally want to run those same scenarios for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these scenarios out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your FeatureSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared scenarios are run for all three fixtures. You can define a behavior function that encapsulates these shared scenarios inside the FeatureSpec that uses them. If they are shared between different FeatureSpecs, however, you could also define them in a separate trait that is mixed into each FeatureSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared scenarios for non-full stacks:
    import org.scalatest.FeatureSpec
    import org.scalatest.GivenWhenThen
    import org.scalatestexamples.helpers.Stack
    
    trait FeatureSpecStackBehaviors { this: FeatureSpec with GivenWhenThen =>
    
      def nonEmptyStack(createNonEmptyStack: => Stack[Int], lastItemAdded: Int) {
    
        scenario("empty is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
    
          When("empty is invoked on the stack")
          Then("empty returns false")
          assert(!stack.empty)
        }
    
        scenario("peek is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
          val size = stack.size
    
          When("peek is invoked on the stack")
          Then("peek returns the last item added")
          assert(stack.peek === lastItemAdded)
    
          And("the size of the stack is the same as before")
          assert(stack.size === size)
        }
    
        scenario("pop is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
          val size = stack.size
    
          When("pop is invoked on the stack")
          Then("pop returns the last item added")
          assert(stack.pop === lastItemAdded)
    
          And("the size of the stack one less than before")
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(createNonFullStack: => Stack[Int]) {
    
        scenario("full is invoked on this non-full stack: " + createNonFullStack.toString) {
    
          Given("a non-full stack")
          val stack = createNonFullStack
    
          When("full is invoked on the stack")
          Then("full returns false")
          assert(!stack.full)
        }
    
        scenario("push is invoked on this non-full stack: " + createNonFullStack.toString) {
    
          Given("a non-full stack")
          val stack = createNonFullStack
          val size = stack.size
    
          When("push is invoked on the stack")
          stack.push(7)
    
          Then("the size of the stack is one greater than before")
          assert(stack.size === size + 1)
    
          And("the top of the stack contains the pushed value")
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but FeatureSpec offers a DSL for the purpose, which looks like this:
    scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    scenariosFor(nonFullStack(stackWithOneItem))
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    scenariosFor(nonEmptyStack) // assuming lastValuePushed is also in scope inside nonEmptyStack
    scenariosFor(nonFullStack)
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    import org.scalatest.FeatureSpec
    import org.scalatest.GivenWhenThen
    import org.scalatestexamples.helpers.Stack
    
    class StackFeatureSpec extends FeatureSpec with GivenWhenThen with FeatureSpecStackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      feature("A Stack is pushed and popped") {
    
        scenario("empty is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("empty is invoked on the stack")
          Then("empty returns true")
          assert(stack.empty)
        }
    
        scenario("peek is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("peek is invoked on the stack")
          Then("peek throws IllegalStateException")
          intercept[IllegalStateException] {
            stack.peek
          }
        }
    
        scenario("pop is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("pop is invoked on the stack")
          Then("pop throws IllegalStateException")
          intercept[IllegalStateException] {
            emptyStack.pop
          }
        }
    
        scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
        scenariosFor(nonFullStack(stackWithOneItem))
    
        scenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
        scenariosFor(nonFullStack(stackWithOneItemLessThanCapacity))
    
        scenario("full is invoked on a full stack") {
    
          Given("an full stack")
          val stack = fullStack
    
          When("full is invoked on the stack")
          Then("full returns true")
          assert(stack.full)
        }
    
        scenariosFor(nonEmptyStack(fullStack, lastValuePushed))
    
        scenario("push is invoked on a full stack") {
    
          Given("an full stack")
          val stack = fullStack
    
          When("push is invoked on the stack")
          Then("push throws IllegalStateException")
          intercept[IllegalStateException] {
            stack.push(10)
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> (new StackFeatureSpec).execute()
    Feature: A Stack is pushed and popped
      Scenario: empty is invoked on an empty stack
        Given an empty stack
        When empty is invoked on the stack
        Then empty returns true
      Scenario: peek is invoked on an empty stack
        Given an empty stack
        When peek is invoked on the stack
        Then peek throws IllegalStateException
      Scenario: pop is invoked on an empty stack
        Given an empty stack
        When pop is invoked on the stack
        Then pop throws IllegalStateException
      Scenario: empty is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: full is invoked on this non-full stack: Stack(9)
        Given a non-full stack
        When full is invoked on the stack
        Then full returns false
      Scenario: push is invoked on this non-full stack: Stack(9)
        Given a non-full stack
        When push is invoked on the stack
        Then the size of the stack is one greater than before
        And the top of the stack contains the pushed value
      Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: full is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-full stack
        When full is invoked on the stack
        Then full returns false
      Scenario: push is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-full stack
        When push is invoked on the stack
        Then the size of the stack is one greater than before
        And the top of the stack contains the pushed value
      Scenario: full is invoked on a full stack
        Given an full stack
        When full is invoked on the stack
        Then full returns true
      Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: push is invoked on a full stack
        Given an full stack
        When push is invoked on the stack
        Then push throws IllegalStateException
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. In a FeatureSpec there is no nesting construct analogous to FunSpec's describe clause. Therefore, you need to do a bit of extra work to ensure that the test names are unique. If a duplicate test name problem shows up in a FeatureSpec, you'll need to pass in a prefix or suffix string to add to each test name. You can pass this string the same way you pass any other data needed by the shared tests, or just call toString on the shared fixture object. This is the approach taken by the previous FeatureSpecStackBehaviors example. Given this FeatureSpecStackBehaviors trait, calling it with the stackWithOneItem fixture, like this:
    scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    
    yields test names: - empty is invoked on this non-empty stack: Stack(9) - peek is invoked on this non-empty stack: Stack(9) - pop is invoked on this non-empty stack: Stack(9) Whereas calling it with the stackWithOneItemLessThanCapacity fixture, like this:
    scenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
    
    yields different test names: - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)

  49. trait FeatureSpecLike extends Suite with TestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class FeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    Implementation trait for class FeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    FeatureSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FeatureSpec into some other class, you can use this trait instead, because class FeatureSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FeatureSpec.

  50. final class Filter extends Serializable

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    Filter whose apply method determines which of the passed tests to run and ignore based on tags to include and exclude passed as as class parameters.

    Filter whose apply method determines which of the passed tests to run and ignore based on tags to include and exclude passed as as class parameters.

    This class handles the org.scalatest.Ignore tag specially, in that its apply method indicates which tests should be ignored based on whether they are tagged with org.scalatest.Ignore. If "org.scalatest.Ignore" is not passed in the tagsToExclude set, it will be implicitly added. However, if the tagsToInclude option is defined, and the contained set does not include "org.scalatest.Ignore", then only those tests that are both tagged with org.scalatest.Ignore and at least one of the tags in the tagsToInclude set will be included in the result of apply and marked as ignored (so long as the test is not also marked with a tag other than org.scalatest.Ignore that is a member of the tagsToExclude set. For example, if SlowAsMolasses is a member of the tagsToInclude set and a test is tagged with both org.scalatest.Ignore and SlowAsMolasses, and SlowAsMolasses appears in the tagsToExclude set, the SlowAsMolasses tag will "overpower" the org.scalatest.Ignore tag, and the test will be filtered out entirely rather than being ignored.

    Exceptions thrown

    IllegalArgumentException if tagsToInclude is defined, but contains an empty set

    NullArgumentException if either tagsToInclude or tagsToExclude are null

  51. trait Finders extends Annotation

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    Annotation used to mark a trait or class as defining a testing style that has a org.scalatest.finders.Finder implementation, which IDEs and other tools can use to discover tests and scopes.

    Annotation used to mark a trait or class as defining a testing style that has a org.scalatest.finders.Finder implementation, which IDEs and other tools can use to discover tests and scopes.

    Note: This is actually an annotation defined in Java, not a Scala trait. It must be defined in Java instead of Scala so it will be accessible at runtime. It has been inserted into Scaladoc by pretending it is a trait.

    This annotation is used to enable different styles of testing, including both native ScalaTest styles and custom user-created styles, to have rich IDE support. The "Finder API" is released separately from ScalaTest proper, because it is only used by tools such as IDEs.

  52. class FlatSpec extends FlatSpecLike

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    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Recommended Usage: Class FlatSpec is a good first step for teams wishing to move from xUnit to BDD, because its structure is flat like xUnit, so simple and familiar, but the test names must be written in a specification style: “X should Y,” “A must B,” etc.

    Trait FlatSpec is so named because your specification text and tests line up flat against the left-side indentation level, with no nesting needed. Here's an example FlatSpec:

    package org.scalatest.examples.flatspec
    
    import org.scalatest.FlatSpec
    
    class SetSpec extends FlatSpec {
    
      behavior of "An empty Set"
    
      it should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    Note: you can use must or can as well as should in a FlatSpec. For example, instead of it should "pop..., you could write it must "pop... or it can "pop....

    Instead of using a behavior of clause, you can alternatively use a shorthand syntax in which you replace the first it with the subject string, like this:

    package org.scalatest.examples.flatspec
    
    import org.scalatest.FlatSpec
    
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    Running either of the two previous three versions of SetSpec in the Scala interpreter would yield:

    An empty Set
    - should have size 0
    - should produce NoSuchElementException when head is invoked
    

    In a FlatSpec you write a one (or more) sentence specification for each bit of behavior you wish to specify and test. Each specification sentence has a "subject," which is sometimes called the system under test (or SUT). The subject is the entity being specified and tested and also serves as the subject of the sentences you write for each test. Often you will want to write multiple tests for the same subject. In a FlatSpec, you name the subject once, with a behavior of clause or its shorthand, then write tests for that subject with it should/must/can "do something" phrases. Each it refers to the most recently declared subject. For example, the four tests shown in this snippet are all testing a stack that contains one item:

    behavior of "A Stack (with one item)"
    
    it should "be non-empty" in {}
    
    it should "return the top item on peek" in {}
    
    it should "not remove the top item on peek" in {}
    
    it should "remove the top item on pop" in {}
    

    The same is true if the tests are written using the shorthand notation:

    "A Stack (with one item)" should "be non-empty" in {}
    
    it should "return the top item on peek" in {}
    
    it should "not remove the top item on peek" in {}
    
    it should "remove the top item on pop" in {}
    

    In a FlatSpec, therefore, to figure out what "it" means, you just scan vertically until you find the most recent use of behavior of or the shorthand notation.

    Because sometimes the subject could be plural, you can alternatively use they instead of it:

    "The combinators" should "be easy to learn" in {}
    
    they should "be efficient" in {}
    
    they should "do something cool" in {}
    

    A FlatSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered while the FlatSpec is in its registration phase. Any attempt to register a test after the FlatSpec has entered its ready phase, i.e., after run has been invoked on the FlatSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using FlatSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, FlatSpec provides a method ignore that can be used instead of it or they to register a test. For example, to temporarily disable the test with the name "An empty Set should produce NoSuchElementException when head is invoked", just change “it” into “ignore,” like this:

    package org.scalatest.examples.flatspec.ignore
    
    import org.scalatest.FlatSpec
    
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      ignore should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the first test and report that the second test was ignored:
    An empty Set
    - should have size 0
    - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    When using shorthand notation, you won't have an it to change into ignore for the first test of each new subject. To ignore such tests, you must instead change in to ignore. For example, to temporarily disable the test with the name "An empty Set should have size 0", change “in” into “ignore” like this:
    package org.scalatest.examples.flatspec.ignoreafter
    
    import org.scalatest.FlatSpec
    
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" ignore {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of StackSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    An empty Set
    - should have size 0 !!! IGNORED !!!
    - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.flatspec.ignoreall
    
    import org.scalatest._
    
    @Ignore
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    An empty Set
    - should have size 0 !!! IGNORED !!!
    - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to FlatSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by FlatSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a specification to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by FlatSpec to pass such information to the reporter. Here's an example:

    package org.scalatest.examples.flatspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FlatSpec with GivenWhenThen {
    
      "A mutable Set" should "allow an element to be added" in {
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this FlatSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    SetSpec:
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    FlatSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FlatSpec that uses markup:

    package org.scalatest.examples.flatspec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FlatSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      "A mutable Set" should "allow an element to be added" in {
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        markup("This test finished with a **bold** statement!")
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.flatspec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FlatSpec {
    
      "A mutable Set" should "allow an element to be added" in {
    
        info("info is recorded")
        markup("markup is *also* recorded")
        note("notes are sent immediately")
        alert("alerts are also sent immediately")
    
        val set = mutable.Set.empty[String]
        set += "clarity"
        assert(set.size === 1)
        assert(set.contains("clarity"))
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    A mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
    - should allow an element to be added
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented. You can mark tests as pending in FlatSpec like this:
    package org.scalatest.examples.flatspec.pending
    
    import org.scalatest._
    
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in (pending)
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of FlatSpec with:
    scala> new SetSpec execute
    
    It will run both tests but report that An empty Set should have size 0 is pending. You'll see:
    An empty Set
    - should have size 0 (pending)
    - should produce NoSuchElementException when head is invoked
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a FlatSpec:
     "The Scala language" must "add correctly" in {
        Given("two integers")
        When("they are added")
        Then("the result is the sum of the two numbers")
        pending
      }
      // ...
    
    Would yield the following output when run in the interpreter:
    The Scala language
    - must add correctly (pending)
      + Given two integers
      + When they are added
      + Then the result is the sum of the two numbers
    
    == Tagging tests == A FlatSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a FlatSpec, groups of tests can optionally be included and/or excluded. To tag a FlatSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for FlatSpecs like this:
    package org.scalatest.examples.flatspec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place FlatSpec tests into groups like this:
    import org.scalatest.FlatSpec
    
    class SetSpec extends FlatSpec {
    
      behavior of "An empty Set"
    
      it should "have size 0" taggedAs(SlowTest) in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" taggedAs(SlowTest, DbTest) in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a FlatSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.flatspec.getfixture
    
    import org.scalatest.FlatSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FlatSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      "Testing" should "be easy" in {
        val f = fixture
        f.builder.append("easy!")
        assert(f.builder.toString === "ScalaTest is easy!")
        assert(f.buffer.isEmpty)
        f.buffer += "sweet"
      }
    
      it should "be fun" in {
        val f = fixture
        f.builder.append("fun!")
        assert(f.builder.toString === "ScalaTest is fun!")
        assert(f.buffer.isEmpty)
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.flatspec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.FlatSpec
    
    class ExampleSpec extends FlatSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      // This test needs the StringBuilder fixture
      "Testing" should "be productive" in new Builder {
        builder.append("productive!")
        assert(builder.toString === "ScalaTest is productive!")
      }
    
      // This test needs the ListBuffer[String] fixture
      "Test code" should "be readable" in new Buffer {
        buffer += ("readable!")
        assert(buffer === List("ScalaTest", "is", "readable!"))
      }
    
      // This test needs both the StringBuilder and ListBuffer
      it should "be clear and concise" in new Builder with Buffer {
        builder.append("clear!")
        buffer += ("concise!")
        assert(builder.toString === "ScalaTest is clear!")
        assert(buffer === List("ScalaTest", "is", "concise!"))
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. That is to say, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:
    package org.scalatest.examples.flatspec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends FlatSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      "This test" should "succeed" in {
        assert(1 + 1 === 2)
      }
    
      it should "fail" in {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes [[org.scalatest.TestData TestData]] such as the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.flatspec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.FlatSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends FlatSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      // This test needs the file fixture
      "Testing" should "be productive" in withFile { (file, writer) =>
        writer.write("productive!")
        writer.flush()
        assert(file.length === 24)
      }
    
      // This test needs the database fixture
      "Test code" should "be readable" in withDatabase { db =>
        db.append("readable!")
        assert(db.toString === "ScalaTest is readable!")
      }
    
      // This test needs both the file and the database
      it should "be clear and concise" in withDatabase { db =>
        withFile { (file, writer) => // loan-fixture methods compose
          db.append("clear!")
          writer.write("concise!")
          writer.flush()
          assert(db.toString === "ScalaTest is clear!")
          assert(file.length === 21)
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.FlatSpec and overriding withFixture(OneArgTest). Each test in a fixture.FlatSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.flatspec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.FlatSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" should "be easy" in { f =>
        f.writer.write("easy!")
        f.writer.flush()
        assert(f.file.length === 18)
      }
    
      it should "be fun" in { f =>
        f.writer.write("fun!")
        f.writer.flush()
        assert(f.file.length === 17)
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.FlatSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.flatspec.beforeandafter
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FlatSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.flatspec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.flatspec.composingbeforeandaftereach
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a FlatSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any FlatSpec that uses them, so that the tests they contain will be registered as tests in that FlatSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your FlatSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the FlatSpec that uses them. If they are shared between different FlatSpecs, however, you could also define them in a separate trait that is mixed into each FlatSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: FlatSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        it should "be non-empty" in {
          assert(!newStack.empty)
        }
    
        it should "return the top item on peek" in {
          assert(newStack.peek === lastItemAdded)
        }
    
        it should "not remove the top item on peek" in {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        it should "remove the top item on pop" in {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        it should "not be full" in {
          assert(!newStack.full)
        }
    
        it should "add to the top on push" in {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but FlatSpec offers a DSL for the purpose, which looks like this:
    it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    it should behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    it should behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    it should behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends FlatSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      "A Stack (when empty)" should "be empty" in {
        assert(emptyStack.empty)
      }
    
      it should "complain on peek" in {
        intercept[IllegalStateException] {
          emptyStack.peek
        }
      }
    
      it should "complain on pop" in {
        intercept[IllegalStateException] {
          emptyStack.pop
        }
      }
    
      "A Stack (with one item)" should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    
      it should behave like nonFullStack(stackWithOneItem)
    
      "A Stack (with one item less than capacity)" should behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
    
      it should behave like nonFullStack(stackWithOneItemLessThanCapacity)
    
      "A Stack (full)" should "be full" in {
        assert(fullStack.full)
      }
    
      it should behave like nonEmptyStack(fullStack, lastValuePushed)
    
      it should "complain on a push" in {
        intercept[IllegalStateException] {
          fullStack.push(10)
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new SharedTestExampleSpec execute
    A Stack (when empty)
    - should be empty
    - should complain on peek
    - should complain on pop
    A Stack (with one item)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (with one item less than capacity)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (full)
    - should be full
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a FlatSpec is to make sure each invocation of a behavior function is in the context of a different set of when, verb (should, must, or can), and that clauses, which will prepend a string to each test name. For example, the following code in a FlatSpec would register a test with the name "A Stack (when empty) should be empty":
      behavior of "A Stack (when empty)"
    
      it should "be empty" in {
        assert(emptyStack.empty)
      }
      // ...
    
    Or, using the shorthand notation:
      "A Stack" when {
        "empty" should {
          "be empty" in {
            assert(emptyStack.empty)
          }
        }
      }
      // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is in the context of a different combination of when, verb, and that clauses.

  53. trait FlatSpecLike extends Suite with TestRegistration with ShouldVerb with MustVerb with CanVerb with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class FlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class FlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    FlatSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FlatSpec into some other class, you can use this trait instead, because class FlatSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FlatSpec.

  54. class FreeSpec extends FreeSpecLike

    Permalink

    Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    FreeSpec is so named because unlike classes such as WordSpec, FlatSpec, and FunSpec, it is enforces no structure on the text. You are free to compose text however you like. (A FreeSpec is like free-verse poetry as opposed to a sonnet or haiku, which defines a structure for the text of the poem.)

    Recommended Usage: Because it gives absolute freedom (and no guidance) on how specification text should be written, FreeSpec is a good choice for teams experienced with BDD and able to agree on how to structure the specification text.

    Here's an example FreeSpec:

    package org.scalatest.examples.freespec
    
    import org.scalatest.FreeSpec
    
    class SetSpec extends FreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    

    In a FreeSpec you write a test with a string followed by in and the body of the test in curly braces, like this:

    "should have size 0" in {
      // ...
    }
    

    You can nest a test inside any number of description clauses, which you write with a string followed by a dash character and a block, like this:

    "A Set" - {
      // ...
    }
    

    You can nest description clauses as deeply as you want. Because the description clause is denoted with an operator, not a word like should, you are free to structure the text however you wish. Here's an example:

    import org.scalatest.FreeSpec
    
    class StackSpec extends FreeSpec {
      "A Stack" - {
        "whenever it is empty" - {
          "certainly ought to" - {
            "be empty" in {
              // ...
            }
            "complain on peek" in {
              // ...
            }
            "complain on pop" in {
              // ...
            }
          }
        }
        "but when full, by contrast, must" - {
          "be full" in {
            // ...
          }
          "complain on push" in {
            // ...
          }
        }
      }
    }
    

    Running the above StackSpec in the interpreter would yield:

    scala> new StackSpec execute
    StackSpec:
    A Stack
      whenever it is empty
        certainly ought to
        - be empty
        - complain on peek
        - complain on pop
      but when full, by contrast, must
      - be full
      - complain on push
    

    A FreeSpec can also be used to write a specification-style test in languages other than English. For example:

    import org.scalatest.FreeSpec
    
    class ComputerRoomRulesSpec extends FreeSpec {
      "Achtung!" - {
        "Alle touristen und non-technischen lookenpeepers!" - {
          "Das machine is nicht fuer fingerpoken und mittengrabben." in {
            // ...
          }
          "Is easy" - {
            "schnappen der springenwerk" in {
              // ...
            }
            "blowenfusen" in {
              // ...
            }
            "und poppencorken mit spitzen sparken." in {
              // ...
            }
          }
          "Das machine is diggen by experten only." in {
            // ...
          }
          "Is nicht fuer gerwerken by das dummkopfen." in {
            // ...
          }
          "Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets." in {
            // ...
          }
          "Relaxen und watchen das blinkenlights." in {
            // ...
          }
        }
      }
    }
    

    Running the above ComputerRoomRulesSpec in the interpreter would yield:

    scala> new ComputerRoomRulesSpec execute
    ComputerRoomRulesSpec:
    Achtung!
      Alle touristen und non-technischen lookenpeepers!
      - Das machine is nicht fuer fingerpoken und mittengrabben.
        Is easy
        - schnappen der springenwerk
        - blowenfusen
        - und poppencorken mit spitzen sparken.
      - Das machine is diggen by experten only.
      - Is nicht fuer gerwerken by das dummkopfen.
      - Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets.
      - Relaxen und watchen das blinkenlights.
    

    A FreeSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered while the FreeSpec is in its registration phase. Any attempt to register a test after the FreeSpec has entered its ready phase, i.e., after run has been invoked on the FreeSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using FreeSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, FreeSpec adds a method ignore to strings that can be used instead of in to register a test. For example, to temporarily disable the test with the name "A Stack should pop values in last-in-first-out order", just change “in” into “ignore,” like this:

    package org.scalatest.examples.freespec.ignore
    
    import org.scalatest.FreeSpec
    
    class SetSpec extends FreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" ignore {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.freespec.ignoreall
    
    import org.scalatest.FreeSpec
    import org.scalatest.Ignore
    
    @Ignore
    class SetSpec extends FreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to FreeSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by FreeSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a specification to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by FreeSpec to pass such information to the reporter. Here's an example:

    package org.scalatest.examples.freespec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FreeSpec with GivenWhenThen {
    
      "A mutable Set" - {
        "should allow an element to be added" in {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          info("That's all folks!")
        }
      }
    }
    

    If you run this FreeSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    FreeSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FreeSpec that uses markup:

    package org.scalatest.examples.freespec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FreeSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      "A mutable Set" - {
        "should allow an element to be added" in {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.freespec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FreeSpec {
    
      "A mutable Set" - {
        "should allow an element to be added" in {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    scala> new SetSpec execute
    SetSpec:
     A mutable Set
       + notes are sent immediately
       + alerts are also sent immediately
     - should allow an element to be added
       + info is recorded
       + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented. You can mark tests as pending in a FreeSpec like this:
    package org.scalatest.examples.freespec.pending
    
    import org.scalatest._
    
    class SetSpec extends FreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in (pending)
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run both tests but report that should have size 0 is pending. You'll see:
    A Set
      when empty
      - should have size 0 (pending)
      - should produce NoSuchElementException when head is invoked
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a FreeSpec:
     "The Scala language" - {
        "should add correctly" in {
          Given("two integers")
          When("they are added")
          Then("the result is the sum of the two numbers")
          pending
        }
        // ...
    
    Would yield the following output when run in the interpreter:
    The Scala language
    - should add correctly (pending)
      + Given two integers
      + When they are added
      + Then the result is the sum of the two numbers
    
    == Tagging tests == A FreeSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a FreeSpec, groups of tests can optionally be included and/or excluded. To tag a FreeSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for FreeSpecs like this:
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could tag FreeSpec tests like this:
    package org.scalatest.examples.freespec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    import org.scalatest.FreeSpec
    
    class SetSpec extends FreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" taggedAs(SlowTest) in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" taggedAs(SlowTest, DbTest) in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a FreeSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.freespec.getfixture
    
    import org.scalatest.FreeSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FreeSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      "Testing" - {
        "should be easy" in {
          val f = fixture
          f.builder.append("easy!")
          assert(f.builder.toString === "ScalaTest is easy!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        "should be fun" in {
          val f = fixture
          f.builder.append("fun!")
          assert(f.builder.toString === "ScalaTest is fun!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.freespec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.FreeSpec
    
    class ExampleSpec extends FreeSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      "Testing" - {
        // This test needs the StringBuilder fixture
        "should be productive" in new Builder {
          builder.append("productive!")
          assert(builder.toString === "ScalaTest is productive!")
        }
      }
    
      "Test code" - {
        // This test needs the ListBuffer[String] fixture
        "should be readable" in new Buffer {
          buffer += ("readable!")
          assert(buffer === List("ScalaTest", "is", "readable!"))
        }
    
        // This test needs both the StringBuilder and ListBuffer
        "should be clear and concise" in new Builder with Buffer {
          builder.append("clear!")
          buffer += ("concise!")
          assert(builder.toString === "ScalaTest is clear!")
          assert(buffer === List("ScalaTest", "is", "concise!"))
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.freespec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends FreeSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      "This test" - {
        "should succeed" in {
          assert(1 + 1 === 2)
        }
    
        "should fail" in {
          assert(1 + 1 === 3)
        }
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.freespec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.FreeSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends FreeSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" - {
        // This test needs the file fixture
        "should be productive" in withFile { (file, writer) =>
          writer.write("productive!")
          writer.flush()
          assert(file.length === 24)
        }
      }
    
      "Test code" - {
        // This test needs the database fixture
        "should be readable" in withDatabase { db =>
          db.append("readable!")
          assert(db.toString === "ScalaTest is readable!")
        }
    
        // This test needs both the file and the database
        "should be clear and concise" in withDatabase { db =>
          withFile { (file, writer) => // loan-fixture methods compose
            db.append("clear!")
            writer.write("concise!")
            writer.flush()
            assert(db.toString === "ScalaTest is clear!")
            assert(file.length === 21)
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.FreeSpec and overriding withFixture(OneArgTest). Each test in a fixture.FreeSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.freespec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.FreeSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" - {
        "should be easy" in { f =>
          f.writer.write("easy!")
          f.writer.flush()
          assert(f.file.length === 18)
        }
    
        "should be fun" in { f =>
          f.writer.write("fun!")
          f.writer.flush()
          assert(f.file.length === 17)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.FreeSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.freespec.beforeandafter
    
    import org.scalatest.FreeSpec
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FreeSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.freespec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FreeSpec with Builder with Buffer {
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.freespec.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FreeSpec with Builder with Buffer {
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a FreeSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any FreeSpec that uses them, so that the tests they contain will be registered as tests in that FreeSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your FreeSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the FreeSpec that uses them. If they are shared between different FreeSpecs, however, you could also define them in a separate trait that is mixed into each FreeSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: FreeSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        "be non-empty" in {
          assert(!newStack.empty)
        }
    
        "return the top item on peek" in {
          assert(newStack.peek === lastItemAdded)
        }
    
        "not remove the top item on peek" in {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        "remove the top item on pop" in {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        "not be full" in {
          assert(!newStack.full)
        }
    
        "add to the top on push" in {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but FreeSpec offers a DSL for the purpose, which looks like this:
    behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends FreeSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      "A Stack" - {
        "when empty" - {
          "should be empty" in {
            assert(emptyStack.empty)
          }
    
          "should complain on peek" in {
            intercept[IllegalStateException] {
              emptyStack.peek
            }
          }
    
          "should complain on pop" in {
            intercept[IllegalStateException] {
              emptyStack.pop
            }
          }
        }
    
        "when it contains one item" - {
          "should" - {
            behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
            behave like nonFullStack(stackWithOneItem)
          }
        }
    
        "when it contains one item less than capacity" - {
          "should" - {
            behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
            behave like nonFullStack(stackWithOneItemLessThanCapacity)
          }
        }
    
        "when full" - {
          "should be full" in {
            assert(fullStack.full)
          }
    
          "should" - {
            behave like nonEmptyStack(fullStack, lastValuePushed)
          }
    
          "should complain on a push" in {
            intercept[IllegalStateException] {
              fullStack.push(10)
            }
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new SharedTestExampleSpec execute
    SharedTestExampleSpec:
    A Stack
      when empty
      - should be empty
      - should complain on peek
      - should complain on pop
      when it contains one item
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
        - not be full
        - add to the top on push
      when it contains one item less than capacity
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
        - not be full
        - add to the top on push
      when full
      - should be full
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
      - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a FreeSpec is to make sure each test is in the context of different surrounding description clauses, because a test's name is the concatenation of its surrounding clauses, followed by the test's text. For example, the following code in a FreeSpec would register a test with the name "A Stack when empty should be empty":
    "A Stack" - {
      "when empty" - {
        "should be empty" in {
          assert(emptyStack.empty)
        }
      }
    }
    // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is in the context of a different surrounding description (dash) clauses.

  55. trait FreeSpecLike extends Suite with TestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class FreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    Implementation trait for class FreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    FreeSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FreeSpec into some other class, you can use this trait instead, because class FreeSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FreeSpec.

  56. class FunSpec extends FunSpecLike

    Permalink

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Recommended Usage: For teams coming from Ruby's RSpec tool, FunSpec will feel familiar and comfortable; More generally, for any team that prefers BDD, FunSpec's nesting and gentle guide to structuring text (with describe and it) provide an excellent general-purpose choice for writing specification-style tests.

    Here's an example FunSpec:

    package org.scalatest.examples.funspec
    
    import org.scalatest.FunSpec
    
    class SetSpec extends FunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    

    A FunSpec contains describe clauses and tests. You define a describe clause with describe, and a test with either it or they. describe, it, and and they are methods, defined in FunSpec, which will be invoked by the primary constructor of SetSpec. A describe clause names, or gives more information about, the subject (class or other entity) you are specifying and testing. In the previous example, "A Set" is the subject under specification and test. With each test you provide a string (the spec text) that specifies one bit of behavior of the subject, and a block of code that tests that behavior. You place the spec text between the parentheses, followed by the test code between curly braces. The test code will be wrapped up as a function passed as a by-name parameter to it (or they), which will register the test for later execution.

    Note: the they method is intended for use when the subject is plural, for example:

    describe("The combinators") {
      they("should be easy to learn") {}
      they("should be efficient") {}
      they("should do something cool") {}
    }
    

    A FunSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered with the it or they methods while the FunSpec is in its registration phase. Any attempt to register a test after the FunSpec has entered its ready phase, i.e., after run has been invoked on the FunSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using FunSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    When you execute a FunSpec, it will send Formatters in the events it sends to the Reporter. ScalaTest's built-in reporters will report these events in such a way that the output is easy to read as an informal specification of the subject being tested. For example, were you to run SetSpec from within the Scala interpreter:

    scala> new SetSpec execute
    

    You would see:

    A Set
      when empty
      - should have size 0
      - should produce NoSuchElementException when head is invoked
    

    Or, to run just the “A Set when empty should have size 0” test, you could pass that test's name, or any unique substring of the name, such as "size 0" or even just "0". Here's an example:

    scala> new SetSuite execute "size 0"
    A Set
      when empty
      - should have size 0
    

    You can also pass to execute a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation for execute (below) and the ScalaTest shell.

    The execute method invokes a run method that takes two parameters. This run method, which actually executes the suite, will usually be invoked by a test runner, such as run, tools.Runner, a build tool, or an IDE.

    Note: FunSpec's syntax is in great part inspired by RSpec, a Ruby BDD framework.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, FunSpec provides registration methods that start with ignore instead of it or they. For example, to temporarily disable the test with the text "should have size 0", just change “it” into “ignore,” like this:

    package org.scalatest.examples.funspec.ignore
    
    import org.scalatest.FunSpec
    
    class SetSpec extends FunSpec {
    
      describe("A Set") {
        describe("when empty") {
          ignore("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.funspec.ignoreall
    
    import org.scalatest.FunSpec
    import org.scalatest.Ignore
    
    @Ignore
    class SetSpec extends FunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to FunSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by FunSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via one of its apply methods. The Informer will then pass the information to the Reporter via an InfoProvided event. Here's an example in which the Informer returned by info is used implicitly by the Given, When, and Then methods of trait GivenWhenThen:

    package org.scalatest.examples.funspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FunSpec with GivenWhenThen {
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          info("That's all folks!")
        }
      }
    }
    

    If you run this FunSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    FunSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FunSpec that uses markup:

    package org.scalatest.examples.funspec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FunSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.funspec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FunSpec {
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    A mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
    - should allow an element to be added
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. You can mark a test as pending in FunSpec by placing "(pending)" after the test name, like this:
    package org.scalatest.examples.funspec.pending
    
    import org.scalatest._
    
    class SetSpec extends FunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") (pending)
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run both tests, but report that the test named "should have size 0" is pending. You'll see:
    A Set
      when empty
      - should have size 0 (pending)
      - should produce NoSuchElementException when head is invoked
    
    == Tagging tests == A FunSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a FunSpec, groups of tests can optionally be included and/or excluded. To tag a FunSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for FunSpecs like this:
    package org.scalatest.examples.funspec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place FunSpec tests into groups like this:
    import org.scalatest.FunSpec
    
    class SetSpec extends FunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0", SlowTest) {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked", SlowTest, DbTest) {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a FunSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.funspec.getfixture
    
    import org.scalatest.FunSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FunSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      describe("Testing") {
        it("should be easy") {
          val f = fixture
          f.builder.append("easy!")
          assert(f.builder.toString === "ScalaTest is easy!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        it("should be fun") {
          val f = fixture
          f.builder.append("fun!")
          assert(f.builder.toString === "ScalaTest is fun!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.funspec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.FunSpec
    
    class ExampleSpec extends FunSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      describe("Testing") {
        // This test needs the StringBuilder fixture
        it("should be productive") {
          new Builder {
            builder.append("productive!")
            assert(builder.toString === "ScalaTest is productive!")
          }
        }
      }
    
      describe("Test code") {
        // This test needs the ListBuffer[String] fixture
        it("should be readable") {
          new Buffer {
            buffer += ("readable!")
            assert(buffer === List("ScalaTest", "is", "readable!"))
          }
        }
    
        // This test needs both the StringBuilder and ListBuffer
        it("should be clear and concise") {
          new Builder with Buffer {
            builder.append("clear!")
            buffer += ("concise!")
            assert(builder.toString === "ScalaTest is clear!")
            assert(buffer === List("ScalaTest", "is", "concise!"))
          }
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.funspec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends FunSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        try super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      describe("This test") {
        it("should succeed") {
          assert(1 + 1 === 2)
        }
    
        it("should fail") {
          assert(1 + 1 === 3)
        }
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.funspec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.FunSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends FunSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      describe("Testing") {
        // This test needs the file fixture
        it("should be productive") {
          withFile { (file, writer) =>
            writer.write("productive!")
            writer.flush()
            assert(file.length === 24)
          }
        }
      }
    
      describe("Test code") {
        // This test needs the database fixture
        it("should be readable") {
          withDatabase { db =>
            db.append("readable!")
            assert(db.toString === "ScalaTest is readable!")
          }
        }
    
        // This test needs both the file and the database
        it("should be clear and concise") {
          withDatabase { db =>
           withFile { (file, writer) => // loan-fixture methods compose
              db.append("clear!")
              writer.write("concise!")
              writer.flush()
              assert(db.toString === "ScalaTest is clear!")
              assert(file.length === 21)
            }
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.Suite and overriding withFixture(OneArgTest). Each test in a fixture.Suite takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.funspec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.FunSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      describe("Testing") {
        it("should be easy") { f =>
          f.writer.write("easy!")
          f.writer.flush()
          assert(f.file.length === 18)
        }
    
        it("should be fun") { f =>
          f.writer.write("fun!")
          f.writer.flush()
          assert(f.file.length === 17)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.FunSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.funspec.beforeandafter
    
    import org.scalatest.FunSpec
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends FunSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.funspec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FunSpec with Builder with Buffer {
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.funspec.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends FunSpec with Builder with Buffer {
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a FunSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any FunSpec that uses them, so that the tests they contain will be registered as tests in that FunSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your FunSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the FunSpec that uses them. If they are shared between different FunSpecs, however, you could also define them in a separate trait that is mixed into each FunSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: FunSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        it("should be non-empty") {
          assert(!newStack.empty)
        }
    
        it("should return the top item on peek") {
          assert(newStack.peek === lastItemAdded)
        }
    
        it("should not remove the top item on peek") {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        it("should remove the top item on pop") {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        it("should not be full") {
          assert(!newStack.full)
        }
    
        it("should add to the top on push") {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but FunSpec offers a DSL for the purpose, which looks like this:
    it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    it should behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    it should behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    it should behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends FunSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      describe("A Stack") {
    
        describe("(when empty)") {
    
          it("should be empty") {
            assert(emptyStack.empty)
          }
    
          it("should complain on peek") {
            intercept[IllegalStateException] {
              emptyStack.peek
            }
          }
    
          it("should complain on pop") {
            intercept[IllegalStateException] {
              emptyStack.pop
            }
          }
        }
    
        describe("(with one item)") {
          it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
          it should behave like nonFullStack(stackWithOneItem)
        }
    
        describe("(with one item less than capacity)") {
          it should behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
          it should behave like nonFullStack(stackWithOneItemLessThanCapacity)
        }
    
        describe("(full)") {
    
          it("should be full") {
            assert(fullStack.full)
          }
    
          it should behave like nonEmptyStack(fullStack, lastValuePushed)
    
          it("should complain on a push") {
            intercept[IllegalStateException] {
              fullStack.push(10)
            }
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new StackSpec execute
    A Stack (when empty)
    - should be empty
    - should complain on peek
    - should complain on pop
    A Stack (with one item)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (with one item less than capacity)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (full)
    - should be full
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a FunSpec is to surround each invocation of a behavior function with a describe clause, which will prepend a string to each test name. For example, the following code in a FunSpec would register a test with the name "A Stack (when empty) should be empty":
      describe("A Stack") {
    
        describe("(when empty)") {
    
          it("should be empty") {
            assert(emptyStack.empty)
          }
          // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is inside a different set of describe clauses.

  57. trait FunSpecLike extends Suite with TestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class FunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class FunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    FunSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FunSpec into some other class, you can use this trait instead, because class FunSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FunSpec.

  58. class FunSuite extends FunSuiteLike

    Permalink

    A suite of tests in which each test is represented as a function value.

    A suite of tests in which each test is represented as a function value. The “Fun” in FunSuite stands for “function.”

    Recommended Usage: For teams coming from xUnit, FunSuite feels comfortable and familiar while still giving some benefits of BDD: FunSuite makes it easy to write descriptive test names, natural to write focused tests, and generates specification-like output that can facilitate communication among stakeholders.

    Here's an example FunSuite:

    package org.scalatest.examples.funsuite
    
    import org.scalatest.FunSuite
    
    class SetSuite extends FunSuite {
    
      test("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    test” is a method, defined in FunSuite, which will be invoked by the primary constructor of SetSuite. You specify the name of the test as a string between the parentheses, and the test code itself between curly braces. The test code is a function passed as a by-name parameter to test, which registers it for later execution.

    A FunSuite's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered with the test method while the FunSuite is in its registration phase. Any attempt to register a test after the FunSuite has entered its ready phase, i.e., after run has been invoked on the FunSuite, will be met with a thrown TestRegistrationClosedException. The recommended style of using FunSuite is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Note: FunSuite was in part inspired by Rehersal, an early test framework for Scala.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, FunSuite provides registration methods that start with ignore instead of test. Here's an example: to temporarily

    package org.scalatest.examples.funsuite.ignore
    
    import org.scalatest.FunSuite
    
    class SetSuite extends FunSuite {
    
      ignore("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of SetSuite with:
    scala> new SetSuite execute
    
    It will run only the second test and report that the first test was ignored:
    SetSuite:
    - An empty Set should have size 0 !!! IGNORED !!!
    - Invoking head on an empty Set should produce NoSuchElementException
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.funsuite.ignoreall
    
    import org.scalatest.FunSuite
    import org.scalatest.Ignore
    
    @Ignore
    class SetSuite extends FunSuite {
    
      test("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSuite in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSuite in the Scala interpreter, you'll see:
    scala> new SetSuite execute
    SetSuite:
    - An empty Set should have size 0 !!! IGNORED !!!
    - Invoking head on an empty Set should produce NoSuchElementException !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to FunSuite's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by FunSuite's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event. Here's an example that shows both a direct use as well as an indirect use through the methods of GivenWhenThen:

    package org.scalatest.examples.funsuite.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends FunSuite with GivenWhenThen {
    
      test("An element can be added to an empty mutable Set") {
    
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this FunSuite from the interpreter, you will see the following output:

    scala> new SetSuite execute
    SetSuite:
    - an element can be added to an empty mutable Set
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks!
    

    Documenters

    FunSuite also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FunSuite that uses markup:

    package org.scalatest.examples.funsuite.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends FunSuite with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      test("An element can be added to an empty mutable Set") {
    
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        markup("This test finished with a **bold** statement!")
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.funsuite.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends FunSuite {
    
      test("An element can be added to an empty mutable Set") {
    
        info("info is recorded")
        markup("markup is *also* recorded")
        note("notes are sent immediately")
        alert("alerts are also sent immediately")
    
        val set = mutable.Set.empty[String]
        set += "clarity"
        assert(set.size === 1)
        assert(set.contains("clarity"))
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSuite:
      + notes are sent immediately
      + alerts are also sent immediately
    - An element can be added to an empty mutable Set
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. Although pending tests may be used more often in specification-style suites, such as org.scalatest.FunSpec, you can also use it in FunSuite, like this:
    package org.scalatest.examples.funsuite.pending
    
    import org.scalatest._
    
    class SetSuite extends FunSuite {
    
      test("An empty Set should have size 0") (pending)
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of SetSuite with:
    scala> new SetSuite execute
    
    It will run both tests, but report that first test is pending. You'll see:
    SetSuite:
    - An empty Set should have size 0 (pending)
    - Invoking head on an empty Set should produce NoSuchElementException
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. == Tagging tests == A FunSuite's tests may be classified into groups by tagging them with string names. As with any suite, when executing a FunSuite, groups of tests can optionally be included and/or excluded. To tag a FunSuite's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for FunSuites like this:
    package org.scalatest.examples.funsuite.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place FunSuite tests into groups like this:
    import org.scalatest.FunSuite
    
    class SetSuite extends FunSuite {
    
      test("An empty Set should have size 0", SlowTest) {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException",
           SlowTest, DbTest) {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a FunSuite in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.funsuite.getfixture
    
    import org.scalatest.FunSuite
    import collection.mutable.ListBuffer
    
    class ExampleSuite extends FunSuite {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      test("Testing should be easy") {
        val f = fixture
        f.builder.append("easy!")
        assert(f.builder.toString === "ScalaTest is easy!")
        assert(f.buffer.isEmpty)
        f.buffer += "sweet"
      }
    
      test("Testing should be fun") {
        val f = fixture
        f.builder.append("fun!")
        assert(f.builder.toString === "ScalaTest is fun!")
        assert(f.buffer.isEmpty)
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.funsuite.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.FunSuite
    
    class ExampleSuite extends FunSuite {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      // This test needs the StringBuilder fixture
      test("Testing should be productive") {
        new Builder {
          builder.append("productive!")
          assert(builder.toString === "ScalaTest is productive!")
        }
      }
    
      // This test needs the ListBuffer[String] fixture
      test("Test code should be readable") {
        new Buffer {
          buffer += ("readable!")
          assert(buffer === List("ScalaTest", "is", "readable!"))
        }
      }
    
      // This test needs both the StringBuilder and ListBuffer
      test("Test code should be clear and concise") {
        new Builder with Buffer {
          builder.append("clear!")
          buffer += ("concise!")
          assert(builder.toString === "ScalaTest is clear!")
          assert(buffer === List("ScalaTest", "is", "concise!"))
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.funsuite.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSuite extends FunSuite {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      test("This test should succeed") {
        assert(1 + 1 === 2)
      }
    
      test("This test should fail") {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    - this test should succeed
    - this test should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.funsuite.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.FunSuite
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSuite extends FunSuite {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      // This test needs the file fixture
      test("Testing should be productive") {
        withFile { (file, writer) =>
          writer.write("productive!")
          writer.flush()
          assert(file.length === 24)
        }
      }
    
      // This test needs the database fixture
      test("Test code should be readable") {
        withDatabase { db =>
          db.append("readable!")
          assert(db.toString === "ScalaTest is readable!")
        }
      }
    
      // This test needs both the file and the database
      test("Test code should be clear and concise") {
        withDatabase { db =>
          withFile { (file, writer) => // loan-fixture methods compose
            db.append("clear!")
            writer.write("concise!")
            writer.flush()
            assert(db.toString === "ScalaTest is clear!")
            assert(file.length === 21)
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.Suite and overriding withFixture(OneArgTest). Each test in a fixture.Suite takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.funsuite.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSuite extends fixture.FunSuite {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      test("Testing should be easy") { f =>
        f.writer.write("easy!")
        f.writer.flush()
        assert(f.file.length === 18)
      }
    
      test("Testing should be fun") { f =>
        f.writer.write("fun!")
        f.writer.flush()
        assert(f.file.length === 17)
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.FunSuite. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.funsuite.beforeandafter
    
    import org.scalatest.FunSuite
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSuite extends FunSuite with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      test("testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.funsuite.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSuite extends FunSuite with Builder with Buffer {
    
      test("Testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("Testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.funsuite.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally buffer.clear()
      }
    }
    
    class ExampleSuite extends FunSuite with Builder with Buffer {
    
      test("Testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("Testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a FunSuite, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any FunSuite that uses them, so that the tests they contain will be registered as tests in that FunSuite. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your FunSuite for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the FunSuite that uses them. If they are shared between different FunSuites, however, you could also define them in a separate trait that is mixed into each FunSuite that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    import org.scalatest.FunSuite
    
    trait FunSuiteStackBehaviors { this: FunSuite =>
    
      def nonEmptyStack(createNonEmptyStack: => Stack[Int], lastItemAdded: Int) {
    
        test("empty is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          assert(!stack.empty)
        }
    
        test("peek is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        test("pop is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(createNonFullStack: => Stack[Int]) {
    
        test("full is invoked on this non-full stack: " + createNonFullStack.toString) {
          val stack = createNonFullStack
          assert(!stack.full)
        }
    
        test("push is invoked on this non-full stack: " + createNonFullStack.toString) {
          val stack = createNonFullStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but FunSuite offers a DSL for the purpose, which looks like this:
    testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    testsFor(nonFullStack(stackWithOneItem))
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    testsFor(nonEmptyStack) // assuming lastValuePushed is also in scope inside nonEmptyStack
    testsFor(nonFullStack)
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    import org.scalatest.FunSuite
    
    class StackFunSuite extends FunSuite with FunSuiteStackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      test("empty is invoked on an empty stack") {
        val stack = emptyStack
        assert(stack.empty)
      }
    
      test("peek is invoked on an empty stack") {
        val stack = emptyStack
        intercept[IllegalStateException] {
          stack.peek
        }
      }
    
      test("pop is invoked on an empty stack") {
        val stack = emptyStack
        intercept[IllegalStateException] {
          emptyStack.pop
        }
      }
    
      testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
      testsFor(nonFullStack(stackWithOneItem))
    
      testsFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
      testsFor(nonFullStack(stackWithOneItemLessThanCapacity))
    
      test("full is invoked on a full stack") {
        val stack = fullStack
        assert(stack.full)
      }
    
      testsFor(nonEmptyStack(fullStack, lastValuePushed))
    
      test("push is invoked on a full stack") {
        val stack = fullStack
        intercept[IllegalStateException] {
          stack.push(10)
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new StackFunSuite execute
    StackFunSuite:
    - empty is invoked on an empty stack
    - peek is invoked on an empty stack
    - pop is invoked on an empty stack
    - empty is invoked on this non-empty stack: Stack(9)
    - peek is invoked on this non-empty stack: Stack(9)
    - pop is invoked on this non-empty stack: Stack(9)
    - full is invoked on this non-full stack: Stack(9)
    - push is invoked on this non-full stack: Stack(9)
    - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - full is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - push is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - full is invoked on a full stack
    - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - push is invoked on a full stack
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. In a FunSuite there is no nesting construct analogous to FunSpec's describe clause. Therefore, you need to do a bit of extra work to ensure that the test names are unique. If a duplicate test name problem shows up in a FunSuite, you'll need to pass in a prefix or suffix string to add to each test name. You can pass this string the same way you pass any other data needed by the shared tests, or just call toString on the shared fixture object. This is the approach taken by the previous FunSuiteStackBehaviors example. Given this FunSuiteStackBehaviors trait, calling it with the stackWithOneItem fixture, like this:
    testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    
    yields test names: - empty is invoked on this non-empty stack: Stack(9) - peek is invoked on this non-empty stack: Stack(9) - pop is invoked on this non-empty stack: Stack(9) Whereas calling it with the stackWithOneItemLessThanCapacity fixture, like this:
    testsFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
    
    yields different test names: - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)

  59. trait FunSuiteLike extends Suite with TestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class FunSuite, which represents a suite of tests in which each test is represented as a function value.

    Implementation trait for class FunSuite, which represents a suite of tests in which each test is represented as a function value.

    FunSuite is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of FunSuite into some other class, you can use this trait instead, because class FunSuite does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of FunSuite.

  60. trait GivenWhenThen extends AnyRef

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    Trait that contains methods named given, when, then, and and, which take a string message and implicit Informer, and forward the message to the informer.

    Trait that contains methods named given, when, then, and and, which take a string message and implicit Informer, and forward the message to the informer.

    Here's an example:

    package org.scalatest.examples.flatspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FlatSpec with GivenWhenThen {
    
      "A mutable Set" should "allow an element to be added" in {
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this SetSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

  61. trait Ignore extends Annotation

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    Annotation used to tag a test, or suite of tests, as ignored.

    Annotation used to tag a test, or suite of tests, as ignored.

    Note: This is actually an annotation defined in Java, not a Scala trait. It must be defined in Java instead of Scala so it will be accessible at runtime. It has been inserted into Scaladoc by pretending it is a trait.

    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:

    package org.scalatest.examples.flatspec.ignoreall
    
    import org.scalatest._
    
    @Ignore
    class SetSpec extends FlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:

    scala> new SetSpec execute
    An empty Set
    - should have size 0 !!! IGNORED !!!
    - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    

    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class somewhat visible, to encourage the developers to eventually fix and un-ignore it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead.

    Another use case for @Ignore is to mark test methods as ignored in traits Spec and fixture.Spec. Here's an example:

    package org.scalatest.examples.spec.ignore
    
    import org.scalatest._
    
    class SetSpec extends Spec {
    
      @Ignore def `an empty Set should have size 0` {
        assert(Set.empty.size === 0)
      }
    
      def `invoking head on an empty Set should produce NoSuchElementException` {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    If you run this version of SetSpec in the Scala interpreter, you'll see that it runs only the second test and reports that the first test was ignored:

    scala> new SetSpec execute
    SetSpec:
    - an empty Set should have size 0 !!! IGNORED !!!
    - invoking head on an empty Set should produce NoSuchElementException
    

  62. trait Informer extends AnyRef

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    Trait to which custom information about a running suite of tests can be reported.

    Trait to which custom information about a running suite of tests can be reported.

    An Informer is essentially used to wrap a Reporter and provide easy ways to send custom information to that Reporter via an InfoProvided event. Informer contains an apply method that takes a string and an optional payload object of type Any. The Informer will forward the passed message string to the Reporter as the message parameter, and the optional payload object as the payload parameter, of an InfoProvided event.

    Here's an example in which the Informer is used both directly via info method of trait FlatSpec and indirectly via the methods of trait GivenWhenThen:

    package org.scalatest.examples.flatspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends FlatSpec with GivenWhenThen {
    
      "A mutable Set" should "allow an element to be added" in {
        given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        when("an element is added")
        set += "clarity"
    
        then("the Set should have size 1")
        assert(set.size === 1)
    
        and("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this SetSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

  63. trait Informing extends AnyRef

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    Trait that contains the info method, which can be used to send info to the reporter.

    Trait that contains the info method, which can be used to send info to the reporter.

  64. trait Inside extends AnyRef

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    Trait containing the inside construct, which allows you to make statements about nested object graphs using pattern matching.

    Trait containing the inside construct, which allows you to make statements about nested object graphs using pattern matching.

    For example, given the following case classes:

    case class Address(street: String, city: String, state: String, zip: String)
    case class Name(first: String, middle: String, last: String)
    case class Record(name: Name, address: Address, age: Int)
    

    You could write:

    inside (rec) { case Record(name, address, age) =>
      inside (name) { case Name(first, middle, last) =>
        first should be ("Sally")
        middle should be ("Ann")
        last should be ("Jones")
      }
      inside (address) { case Address(street, city, state, zip) =>
        street should startWith ("25")
        city should endWith ("Angeles")
        state should equal ("CA")
        zip should be ("12345")
      }
      age should be < 99
    }
    

    If an assertion fails, the error message will include the toString of each value passed to inside clauses enclosing the failed assertion. For example, if rec in the previous expression was defined like this:

    val rec = Record(
      Name("Sally", "Anna", "Jones"),
      Address("25 Main St", "Los Angeles", "CA", "12345"),
      38
    )
    

    The error message will read:

    "Ann[a]" was not equal to "Ann[]", inside Name(Sally,Anna,Jones),
    inside Record(Name(Sally,Anna,Jones),Address(25 Main St,Los Angeles,CA,12345),38)
    

  65. trait Inspectors extends AnyRef

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    Provides nestable inspector methods (or just inspectors) that enable assertions to be made about collections.

    Provides nestable inspector methods (or just inspectors) that enable assertions to be made about collections.

    For example, the forAll method enables you to state that something should be true about all elements of a collection, such as that all elements should be positive:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import Assertions._
    import Assertions._
    
    scala> import Inspectors._
    import Inspectors._
    
    scala> val xs = List(1, 2, 3, 4, 5)
    xs: List[Int] = List(1, 2, 3, 4, 5)
    
    scala> forAll (xs) { x => assert(x > 0) }
    

    Or, with matchers:

    scala> import Matchers._
    import Matchers._
    
    scala> forAll (xs) { x => x should be > 0 }
    

    To make assertions about nested collections, you can nest the inspector method invocations. For example, given the following list of lists of Int:

    scala> val yss =
         |   List(
         |     List(1, 2, 3),
         |     List(1, 2, 3),
         |     List(1, 2, 3)
         |   )
    yss: List[List[Int]] = List(List(1, 2, 3), List(1, 2, 3), List(1, 2, 3))
    

    You can assert that all Int elements in all nested lists are positive by nesting two forAll method invocations, like this:

    scala> forAll (yss) { ys =>
         |   forAll (ys) { y => y should be > 0 }
         | }
    

    The full list of inspector methods are:

    • forAll - succeeds if the assertion holds true for every element
    • forAtLeast - succeeds if the assertion holds true for at least the specified number of elements
    • forAtMost - succeeds if the assertion holds true for at most the specified number of elements
    • forBetween - succeeds if the assertion holds true for between the specified minimum and maximum number of elements, inclusive
    • forEvery - same as forAll, but lists all failing elements if it fails (whereas forAll just reports the first failing element)
    • forExactly - succeeds if the assertion holds true for exactly the specified number of elements

    The error messages produced by inspector methods are designed to make sense no matter how deeply you nest the method invocations. Here's an example of a nested inspection that fails and the resulting error message:

    scala> forAll (yss) { ys =>
         |   forAll (ys) { y => y should be < 2 }
         | }
    org.scalatest.exceptions.TestFailedException: forAll failed, because:
      at index 0, forAll failed, because:
        at index 1, 2 was not less than 2 (<console>:20)
      in List(1, 2, 3) (<console>:20)
    in List(List(1, 2, 3), List(1, 2, 3), List(1, 2, 3))
         at org.scalatest.InspectorsHelper$.forAll(Inspectors.scala:146)
         ...
    

    One way the error message is designed to help you understand the error is by using indentation that mimics the indentation of the source code (optimistically assuming the source will be nicely indented). The error message above indicates the outer forAll failed because its initial List (i.e., at index 0) failed the assertion, which was that all elements of that initial List[Int] at index 0 should be less than 2. This assertion failed because index 1 of that inner list contained the value 2, which was indeed “not less than 2.” The error message for the inner list is an indented line inside the error message for the outer list. The actual contents of each list are displayed at the end in inspector error messages, also indented appropriately. The actual contents are placed at the end so that for very large collections, the contents will not drown out and make it difficult to find the messages that describe actual causes of the failure.

    The forAll and forEvery methods are similar in that both succeed only if the assertion holds for all elements of the collection. They differ in that forAll will only report the first element encountered that failed the assertion, but forEvery will report all elements that fail the assertion. The tradeoff is that while forEvery gives more information, it may take longer to run because it must inspect every element of the collection. The forAll method can simply stop inspecting once it encounters the first failing element. Here's an example that shows the difference in the forAll and forEvery error messages:

    scala> forAll (xs) { x => x should be < 3 }
    org.scalatest.exceptions.TestFailedException: forAll failed, because:
      at index 2, 3 was not less than 3 (<console>:18)
    in List(1, 2, 3, 4, 5)
         at org.scalatest.InspectorsHelper$.forAll(Inspectors.scala:146)
         ...
    
    scala> forEvery (xs) { x => x should be < 3 }
    org.scalatest.exceptions.TestFailedException: forEvery failed, because:
      at index 2, 3 was not less than 3 (<console>:18),
      at index 3, 4 was not less than 3 (<console>:18),
      at index 4, 5 was not less than 3 (<console>:18)
    in List(1, 2, 3, 4, 5)
         at org.scalatest.InspectorsHelper$.forEvery(Inspectors.scala:226)
         ...
    

    Note that if you're using matchers, you can alternatively use inspector shorthands for writing non-nested inspections. Here's an example:

    scala> all (xs) should be > 3
    org.scalatest.exceptions.TestFailedException: 'all' inspection failed, because:
      at index 0, 1 was not greater than 3
    in List(1, 2, 3, 4, 5)
         at org.scalatest.InspectorsHelper$.forAll(Inspectors.scala:146)
    

    You can use Inspectors on any scala.collection.GenTraversable, java.util.Collection, java.util.Map (with Entry), Array, or String. Here are some examples:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import Inspectors._
    import Inspectors._
    
    scala> import Matchers._
    import Matchers._
    
    scala> forAll (Array(1, 2, 3)) { e => e should be < 5 }
    
    scala> import collection.JavaConverters._
    import collection.JavaConverters._
    
    scala> val js = List(1, 2, 3).asJava
    js: java.util.List[Int] = [1, 2, 3]
    
    scala> forAll (js) { j => j should be < 5 }
    
    scala> val jmap = Map("a" -> 1, "b" -> 2).asJava
    jmap: java.util.Map[String,Int] = {a=1, b=2}
    
    scala> forAtLeast(1, jmap) { e => e shouldBe Entry("b", 2) }
    
    scala> forAtLeast(2, "hello, world!") { c => c shouldBe 'o' }
    

  66. trait LoneElement extends AnyRef

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    Trait that provides an implicit conversion that adds to collection types a loneElement method, which will return the value of the lone element if the collection does indeed contain one and only one element, or throw TestFailedException if not.

    Trait that provides an implicit conversion that adds to collection types a loneElement method, which will return the value of the lone element if the collection does indeed contain one and only one element, or throw TestFailedException if not.

    This construct allows you to express in one statement that a collection should contain one and only one element and that the element value should meet some expectation. Here's an example:

    set.loneElement should be > 9
    

    Or, using an assertion instead of a matcher expression:

    assert(set.loneElement > 9)
    

    The loneElement syntax can be used with any collection type C for which an implicit Collecting[C] is available. ScalaTest provides implicit Collecting instances for scala.collection.GenTraversable, Array, and java.util.Collection. You can enable the loneElement syntax on other collection types by defining an implicit Collecting instances for those types.

    If you want to use loneElement with a java.util.Map, first transform it to a set of entries with entrySet, and if helpful, use ScalaTest's Entry class:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import LoneElement._
    import LoneElement._
    
    scala> import Matchers._
    import Matchers._
    
    scala> val jmap = new java.util.HashMap[String, Int]
    jmap: java.util.HashMap[String,Int] = {}
    
    scala> jmap.put("one", 1)
    res0: Int = 0
    
    scala> jmap.entrySet.loneElement should be (Entry("one", 1))
    

  67. trait Matchers extends Assertions with Tolerance with ShouldVerb with MatcherWords with Explicitly

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    Trait that provides a domain specific language (DSL) for expressing assertions in tests using the word should.

    Trait that provides a domain specific language (DSL) for expressing assertions in tests using the word should.

    For example, if you mix Matchers into a suite class, you can write an equality assertion in that suite like this:

    result should equal (3)
    

    Here result is a variable, and can be of any type. If the object is an Int with the value 3, execution will continue (i.e., the expression will result in the unit value, ()). Otherwise, a TestFailedException will be thrown with a detail message that explains the problem, such as "7 did not equal 3". This TestFailedException will cause the test to fail.

    Here is a table of contents for this documentation:

    Trait MustMatchers is an alternative to Matchers that provides the exact same meaning, syntax, and behavior as Matchers, but uses the verb must instead of should. The two traits differ only in the English semantics of the verb: should is informal, making the code feel like conversation between the writer and the reader; must is more formal, making the code feel more like a written specification.

    Checking equality with matchers

    ScalaTest matchers provides five different ways to check equality, each designed to address a different need. They are:

    result should equal (3) // can customize equality
    result should === (3)   // can customize equality and enforce type constraints
    result should be (3)    // cannot customize equality, so fastest to compile
    result shouldEqual 3    // can customize equality, no parentheses required
    result shouldBe 3       // cannot customize equality, so fastest to compile, no parentheses required
    

    The “left should equal (right)” syntax requires an org.scalactic.Equality[L] to be provided (either implicitly or explicitly), where L is the left-hand type on which should is invoked. In the "left should equal (right)" case, for example, L is the type of left. Thus if left is type Int, the "left should equal (right)" statement would require an Equality[Int].

    By default, an implicit Equality[T] instance is available for any type T, in which equality is implemented by simply invoking == on the left value, passing in the right value, with special treatment for arrays. If either left or right is an array, deep will be invoked on it before comparing with ==. Thus, the following expression will yield false, because Array's equals method compares object identity:

    Array(1, 2) == Array(1, 2) // yields false
    

    The next expression will by default not result in a TestFailedException, because default Equality[Array[Int]] compares the two arrays structurally, taking into consideration the equality of the array's contents:

    Array(1, 2) should equal (Array(1, 2)) // succeeds (i.e., does not throw TestFailedException)
    

    If you ever do want to verify that two arrays are actually the same object (have the same identity), you can use the be theSameInstanceAs syntax, described below.

    You can customize the meaning of equality for a type when using "should equal," "should ===," or shouldEqual syntax by defining implicit Equality instances that will be used instead of default Equality. You might do this to normalize types before comparing them with ==, for instance, or to avoid calling the == method entirely, such as if you want to compare Doubles with a tolerance. For an example, see the main documentation of trait Equality.

    You can always supply implicit parameters explicitly, but in the case of implicit parameters of type Equality[T], Scalactic provides a simple "explictly" DSL. For example, here's how you could explicitly supply an Equality[String] instance that normalizes both left and right sides (which must be strings), by transforming them to lowercase:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> import org.scalactic.Explicitly._
    import org.scalactic.Explicitly._
    
    scala> import org.scalactic.StringNormalizations._
    import org.scalactic.StringNormalizations._
    
    scala> "Hi" should equal ("hi") (after being lowerCased)
    

    The after being lowerCased expression results in an Equality[String], which is then passed explicitly as the second curried parameter to equal. For more information on the explictly DSL, see the main documentation for trait Explicitly.

    The "should be" and shouldBe syntax do not take an Equality[T] and can therefore not be customized. They always use the default approach to equality described above. As a result, "should be" and shouldBe will likely be the fastest-compiling matcher syntax for equality comparisons, since the compiler need not search for an implicit Equality[T] each time.

    The should === syntax (and its complement, should !==) can be used to enforce type constraints at compile-time between the left and right sides of the equality comparison. Here's an example:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> import org.scalactic.TypeCheckedTripleEquals._
    import org.scalactic.TypeCheckedTripleEquals._
    
    scala> Some(2) should === (2)
    <console>:17: error: types Some[Int] and Int do not adhere to the equality constraint
    selected for the === and !== operators; the missing implicit parameter is of
    type org.scalactic.CanEqual[Some[Int],Int]
                  Some(2) should === (2)
                          ^
    

    By default, the "Some(2) should === (2)" statement would fail at runtime. By mixing in the equality constraints provided by TypeCheckedTripleEquals, however, the statement fails to compile. For more information and examples, see the main documentation for trait TypeCheckedTripleEquals.

    Checking size and length

    You can check the size or length of any type of object for which it makes sense. Here's how checking for length looks:

    result should have length 3
    

    Size is similar:

    result should have size 10
    

    The length syntax can be used with String, Array, any scala.collection.GenSeq, any java.util.List, and any type T for which an implicit Length[T] type class is available in scope. Similarly, the size syntax can be used with Array, any scala.collection.GenTraversable, any java.util.Collection, any java.util.Map, and any type T for which an implicit Size[T] type class is available in scope. You can enable the length or size syntax for your own arbitrary types, therefore, by defining Length or Size type classes for those types.

    In addition, the length syntax can be used with any object that has a field or method named length or a method named getLength. Similarly, the size syntax can be used with any object that has a field or method named size or a method named getSize. The type of a length or size field, or return type of a method, must be either Int or Long. Any such method must take no parameters. (The Scala compiler will ensure at compile time that the object on which should is being invoked has the appropriate structure.)

    Checking strings

    You can check for whether a string starts with, ends with, or includes a substring like this:

    string should startWith ("Hello")
    string should endWith ("world")
    string should include ("seven")
    

    You can check for whether a string starts with, ends with, or includes a regular expression, like this:

    string should startWith regex "Hel*o"
    string should endWith regex "wo.ld"
    string should include regex "wo.ld"
    

    And you can check whether a string fully matches a regular expression, like this:

    string should fullyMatch regex """(-)?(\d+)(\.\d*)?"""
    

    The regular expression passed following the regex token can be either a String or a scala.util.matching.Regex.

    With the startWith, endWith, include, and fullyMatch tokens can also be used with an optional specification of required groups, like this:

    "abbccxxx" should startWith regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "xxxabbcc" should endWith regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "xxxabbccxxx" should include regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "abbcc" should fullyMatch regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    

    You can check whether a string is empty with empty:

    s shouldBe empty
    

    You can also use most of ScalaTest's matcher syntax for collections on String by treating the Strings as collections of characters. For examples, see the Strings and Arrays as collections section below.

    Greater and less than

    You can check whether any type for which an implicit Ordering[T] is available is greater than, less than, greater than or equal, or less than or equal to a value of type T. The syntax is:

    one should be < 7
    one should be > 0
    one should be <= 7
    one should be >= 0
    

    Checking Boolean properties with be

    If an object has a method that takes no parameters and returns boolean, you can check it by placing a Symbol (after be) that specifies the name of the method (excluding an optional prefix of "is"). A symbol literal in Scala begins with a tick mark and ends at the first non-identifier character. Thus, 'traversableAgain results in a Symbol object at runtime, as does 'completed and 'file. Here's an example:

    iter shouldBe 'traversableAgain
    

    Given this code, ScalaTest will use reflection to look on the object referenced from emptySet for a method that takes no parameters and results in Boolean, with either the name empty or isEmpty. If found, it will invoke that method. If the method returns true, execution will continue. But if it returns false, a TestFailedException will be thrown that will contain a detail message, such as:

    non-empty iterator was not traversableAgain
    

    This be syntax can be used with any reference (AnyRef) type. If the object does not have an appropriately named predicate method, you'll get a TestFailedException at runtime with a detailed message that explains the problem. (For the details on how a field or method is selected during this process, see the documentation for BeWord.)

    If you think it reads better, you can optionally put a or an after be. For example, java.io.File has two predicate methods, isFile and isDirectory. Thus with a File object named temp, you could write:

    temp should be a 'file
    

    Or, given java.awt.event.KeyEvent has a method isActionKey that takes no arguments and returns Boolean, you could assert that a KeyEvent is an action key with:

    keyEvent should be an 'actionKey
    

    If you prefer to check Boolean properties in a type-safe manner, you can use a BePropertyMatcher. This would allow you to write expressions such as:

    xs shouldBe traversableAgain
    temp should be a file
    keyEvent should be an actionKey
    

    These expressions would fail to compile if should is used on an inappropriate type, as determined by the type parameter of the BePropertyMatcher being used. (For example, file in this example would likely be of type BePropertyMatcher[java.io.File]. If used with an appropriate type, such an expression will compile and at run time the Boolean property method or field will be accessed directly; i.e., no reflection will be used. See the documentation for BePropertyMatcher for more information.

    Using custom BeMatchers

    If you want to create a new way of using be, which doesn't map to an actual property on the type you care about, you can create a BeMatcher. You could use this, for example, to create BeMatcher[Int] called odd, which would match any odd Int, and even, which would match any even Int. Given this pair of BeMatchers, you could check whether an Int was odd or even with expressions like:

    num shouldBe odd
    num should not be even
    

    For more information, see the documentation for BeMatcher.

    Checking object identity

    If you need to check that two references refer to the exact same object, you can write:

    ref1 should be theSameInstanceAs ref2
    

    Checking an object's class

    If you need to check that an object is an instance of a particular class or trait, you can supply the type to “be a” or “be an”:

    result1 shouldBe a [Tiger]
    result1 should not be an [Orangutan]
    

    Because type parameters are erased on the JVM, we recommend you insert an underscore for any type parameters when using this syntax. Both of the following test only that the result is an instance of List[_], because at runtime the type parameter has been erased:

    result shouldBe a [List[_]] // recommended
    result shouldBe a [List[Fruit]] // discouraged
    

    Checking numbers against a range

    Often you may want to check whether a number is within a range. You can do that using the +- operator, like this:

    sevenDotOh should equal (6.9 +- 0.2)
    sevenDotOh should === (6.9 +- 0.2)
    sevenDotOh should be (6.9 +- 0.2)
    sevenDotOh shouldEqual 6.9 +- 0.2
    sevenDotOh shouldBe 6.9 +- 0.2
    

    Any of these expressions will cause a TestFailedException to be thrown if the floating point value, sevenDotOh is outside the range 6.7 to 7.1. You can use +- with any type T for which an implicit Numeric[T] exists, such as integral types:

    seven should equal (6 +- 2)
    seven should === (6 +- 2)
    seven should be (6 +- 2)
    seven shouldEqual 6 +- 2
    seven shouldBe 6 +- 2
    

    Checking for emptiness

    You can check whether an object is "empty", like this:

    traversable shouldBe empty
    javaMap should not be empty
    

    The empty token can be used with any type L for which an implicit Emptiness[L] exists. The Emptiness companion object provides implicits for GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E], and Option[E]. In addition, the Emptiness companion object provides structural implicits for types that declare an isEmpty method that returns a Boolean. Here are some examples:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> List.empty shouldBe empty
    
    scala> None shouldBe empty
    
    scala> Some(1) should not be empty
    
    scala> "" shouldBe empty
    
    scala> new java.util.HashMap[Int, Int] shouldBe empty
    
    scala> new { def isEmpty = true} shouldBe empty
    
    scala> Array(1, 2, 3) should not be empty
    

    Working with "containers"

    You can check whether a collection contains a particular element like this:

    traversable should contain ("five")
    

    The contain syntax shown above can be used with any type C that has a "containing" nature, evidenced by an implicit org.scalatest.enablers.Containing[L], where L is left-hand type on which should is invoked. In the Containing companion object, implicits are provided for types GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E], and Option[E]. Here are some examples:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> List(1, 2, 3) should contain (2)
    
    scala> Map('a' -> 1, 'b' -> 2, 'c' -> 3) should contain ('b' -> 2)
    
    scala> Set(1, 2, 3) should contain (2)
    
    scala> Array(1, 2, 3) should contain (2)
    
    scala> "123" should contain ('2')
    
    scala> Some(2) should contain (2)
    

    ScalaTest's implicit methods that provide the Containing[L] type classes require an Equality[E], where E is an element type. For example, to obtain a Containing[Array[Int]] you must supply an Equality[Int], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Containing[L], implicit conversions are provided in the Containing companion object from Equality[E] to the various types of containers of E. Here's an example:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> List("Hi", "Di", "Ho") should contain ("ho")
    org.scalatest.exceptions.TestFailedException: List(Hi, Di, Ho) did not contain element "ho"
            at ...
    
    scala> import org.scalactic.Explicitly._
    import org.scalactic.Explicitly._
    
    scala> import org.scalactic.StringNormalizations._
    import org.scalactic.StringNormalizations._
    
    scala> (List("Hi", "Di", "Ho") should contain ("ho")) (after being lowerCased)
    

    Note that when you use the explicitly DSL with contain you need to wrap the entire contain expression in parentheses, as shown here.

    (List("Hi", "Di", "Ho") should contain ("ho")) (after being lowerCased)
    ^                                            ^
    

    In addition to determining whether an object contains another object, you can use contain to make other determinations. For example, the contain oneOf syntax ensures that one and only one of the specified elements are contained in the containing object:

    List(1, 2, 3, 4, 5) should contain oneOf (5, 7, 9)
    Some(7) should contain oneOf (5, 7, 9)
    "howdy" should contain oneOf ('a', 'b', 'c', 'd')
    

    Note that if multiple specified elements appear in the containing object, oneOf will fail:

    scala> List(1, 2, 3) should contain oneOf (2, 3, 4)
    org.scalatest.exceptions.TestFailedException: List(1, 2, 3) did not contain one (and only one) of (2, 3, 4)
            at ...
    

    If you really want to ensure one or more of the specified elements are contained in the containing object, use atLeastOneOf, described below, instead of oneOf. Keep in mind, oneOf means "exactly one of."

    Note also that with any contain syntax, you can place custom implicit Equality[E] instances in scope to customize how containership is determined, or use the explicitly DSL. Here's an example:

    (Array("Doe", "Ray", "Me") should contain oneOf ("X", "RAY", "BEAM")) (after being lowerCased)
    

    If you have a collection of elements that you'd like to use in a "one of" comparison, you can use "oneElementOf," like this:

    List(1, 2, 3, 4, 5) should contain oneElementOf List(5, 7, 9)
    Some(7) should contain oneElementOf Vector(5, 7, 9)
    "howdy" should contain oneElementOf Set('a', 'b', 'c', 'd')
    (Array("Doe", "Ray", "Me") should contain oneElementOf List("X", "RAY", "BEAM")) (after being lowerCased)
    

    The contain noneOf syntax does the opposite of oneOf: it ensures none of the specified elements are contained in the containing object:

    List(1, 2, 3, 4, 5) should contain noneOf (7, 8, 9)
    Some(0) should contain noneOf (7, 8, 9)
    "12345" should contain noneOf ('7', '8', '9')
    

    If you have a collection of elements that you'd like to use in a "none of" comparison, you can use "noElementsOf," like this:

    List(1, 2, 3, 4, 5) should contain noElementsOf List(7, 8, 9)
    Some(0) should contain noElementsOf Vector(7, 8, 9)
    "12345" should contain noElementsOf Set('7', '8', '9')
    

    Working with "aggregations"

    As mentioned, the "contain," "contain oneOf," and "contain noneOf" syntax requires a Containing[L] be provided, where L is the left-hand type. Other contain syntax, which will be described in this section, requires an Aggregating[L] be provided, where again L is the left-hand type. (An Aggregating[L] instance defines the "aggregating nature" of a type L.) The reason, essentially, is that contain syntax that makes sense for Option is enabled by Containing[L], whereas syntax that does not make sense for Option is enabled by Aggregating[L]. For example, it doesn't make sense to assert that an Option[Int] contains all of a set of integers, as it could only ever contain one of them. But this does make sense for a type such as List[Int] that can aggregate zero to many integers.

    The Aggregating companion object provides implicit instances of Aggregating[L] for types GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E]. Note that these are the same types as are supported with Containing, but with Option[E] missing. Here are some examples:

    The contain atLeastOneOf syntax, for example, works for any type L for which an Aggregating[L] exists. It ensures that at least one of (i.e., one or more of) the specified objects are contained in the containing object:

    List(1, 2, 3) should contain atLeastOneOf (2, 3, 4)
    Array(1, 2, 3) should contain atLeastOneOf (3, 4, 5)
    "abc" should contain atLeastOneOf ('c', 'a', 't')
    

    Similar to Containing[L], the implicit methods that provide the Aggregating[L] instances require an Equality[E], where E is an element type. For example, to obtain a Aggregating[Vector[String]] you must supply an Equality[String], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Aggregating[L], implicit conversions are provided in the Aggregating companion object from Equality[E] to the various types of aggregations of E. Here's an example:

    (Vector(" A", "B ") should contain atLeastOneOf ("a ", "b", "c")) (after being lowerCased and trimmed)
    

    If you have a collection of elements that you'd like to use in an "at least one of" comparison, you can use "atLeastOneElementOf," like this:

    List(1, 2, 3) should contain atLeastOneElementOf List(2, 3, 4)
    Array(1, 2, 3) should contain atLeastOneElementOf Vector(3, 4, 5)
    "abc" should contain atLeastOneElementOf Set('c', 'a', 't')
    (Vector(" A", "B ") should contain atLeastOneElementOf List("a ", "b", "c")) (after being lowerCased and trimmed)
    

    The "contain atMostOneOf" syntax lets you specify a set of objects at most one of which should be contained in the containing object:

    List(1, 2, 3, 4, 5) should contain atMostOneOf (5, 6, 7)
    

    If you have a collection of elements that you'd like to use in a "at most one of" comparison, you can use "atMostOneElementOf," like this:

    List(1, 2, 3, 4, 5) should contain atMostOneElementOf Vector(5, 6, 7)
    

    The "contain allOf" syntax lets you specify a set of objects that should all be contained in the containing object:

    List(1, 2, 3, 4, 5) should contain allOf (2, 3, 5)
    

    If you have a collection of elements that you'd like to use in a "all of" comparison, you can use "allElementsOf," like this:

    List(1, 2, 3, 4, 5) should contain allElementsOf Array(2, 3, 5)
    

    The "contain only" syntax lets you assert that the containing object contains only the specified objects, though it may contain more than one of each:

    List(1, 2, 3, 2, 1) should contain only (1, 2, 3)
    

    The "contain theSameElementsAs" and "contain theSameElementsInOrderAs syntax differ from the others in that the right hand side is a GenTraversable[_] rather than a varargs of Any. (Note: in a future 2.0 milestone release, possibly 2.0.M6, these will likely be widened to accept any type R for which an Aggregating[R] exists.)

    The "contain theSameElementsAs" syntax lets you assert that two aggregations contain the same objects:

    List(1, 2, 2, 3, 3, 3) should contain theSameElementsAs Vector(3, 2, 3, 1, 2, 3)
    

    The number of times any family of equal objects appears must also be the same in both the left and right aggregations. The specified objects may appear multiple times, but must appear in the order they appear in the right-hand list. For example, if the last 3 element is left out of the right-hand list in the previous example, the expression would fail because the left side has three 3's and the right hand side has only two:

    List(1, 2, 2, 3, 3, 3) should contain theSameElementsAs Vector(3, 2, 3, 1, 2)
    org.scalatest.exceptions.TestFailedException: List(1, 2, 2, 3, 3, 3) did not contain the same elements as Vector(3, 2, 3, 1, 2)
            at ...
    

    Note that no onlyElementsOf matcher is provided, because it would have the same behavior as theSameElementsAs. (I.e., if you were looking for onlyElementsOf, please use theSameElementsAs instead.)

    Working with "sequences"

    The rest of the contain syntax, which will be described in this section, requires a Sequencing[L] be provided, where again L is the left-hand type. (A Sequencing[L] instance defines the "sequencing nature" of a type L.) The reason, essentially, is that contain syntax that implies an "order" of elements makes sense only for types that place elements in a sequence. For example, it doesn't make sense to assert that a Map[String, Int] or Set[Int] contains all of a set of integers in a particular order, as these types don't necessarily define an order for their elements. But this does make sense for a type such as Seq[Int] that does define an order for its elements.

    The Sequencing companion object provides implicit instances of Sequencing[L] for types GenSeq[E], java.util.List[E], String, and Array[E]. Here are some examples:

    Similar to Containing[L], the implicit methods that provide the Aggregating[L] instances require an Equality[E], where E is an element type. For example, to obtain a Aggregating[Vector[String]] you must supply an Equality[String], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Aggregating[L], implicit conversions are provided in the Aggregating companion object from Equality[E] to the various types of aggregations of E. Here's an example:

    The "contain inOrderOnly" syntax lets you assert that the containing object contains only the specified objects, in order. The specified objects may appear multiple times, but must appear in the order they appear in the right-hand list. Here's an example:

    List(1, 2, 2, 3, 3, 3) should contain inOrderOnly (1, 2, 3)
    

    The "contain inOrder" syntax lets you assert that the containing object contains only the specified objects in order, like inOrderOnly, but allows other objects to appear in the left-hand aggregation as well: contain more than one of each:

    List(0, 1, 2, 2, 99, 3, 3, 3, 5) should contain inOrder (1, 2, 3)
    

    If you have a collection of elements that you'd like to use in a "in order" comparison, you can use "inOrderElementsOf," like this:

    List(0, 1, 2, 2, 99, 3, 3, 3, 5) should contain inOrderElementsOf Array(1, 2, 3)
    

    Note that "order" in inOrder, inOrderOnly, and theSameElementsInOrderAs (described below) in the Aggregation[L] instances built-in to ScalaTest is defined as "iteration order".

    Lastly, the "contain theSameElementsInOrderAs" syntax lets you assert that two aggregations contain the same exact elements in the same (iteration) order:

    List(1, 2, 3) should contain theSameElementsInOrderAs collection.mutable.TreeSet(3, 2, 1)
    

    The previous assertion succeeds because the iteration order of aTreeSet is the natural ordering of its elements, which in this case is 1, 2, 3. An iterator obtained from the left-hand List will produce the same elements in the same order.

    Note that no inOrderOnlyElementsOf matcher is provided, because it would have the same behavior as theSameElementsInOrderAs. (I.e., if you were looking for inOrderOnlyElementsOf, please use theSameElementsInOrderAs instead.)

    Working with "sortables"

    You can also ask whether the elements of "sortable" objects (such as Arrays, Java Lists, and GenSeqs) are in sorted order, like this:

    List(1, 2, 3) shouldBe sorted
    

    Working with iterators

    Althought it seems desireable to provide similar matcher syntax for Scala and Java iterators to that provided for sequences like Seqs, Array, and java.util.List, the ephemeral nature of iterators makes this problematic. Some syntax (such as should contain) is relatively straightforward to support on iterators, but other syntax (such as, for example, Inspector expressions on nested iterators) is not. Rather than allowing inconsistencies between sequences and iterators in the API, we chose to not support any such syntax directly on iterators:

    scala> val it = List(1, 2, 3).iterator
    it: Iterator[Int] = non-empty iterator
    
    scala> it should contain (2)
    <console>:15: error: could not find implicit value for parameter typeClass1: org.scalatest.enablers.Containing[Iterator[Int]]
               it should contain (2)
                  ^
    

    Instead, you will need to convert your iterators to a sequence explicitly before using them in matcher expressions:

    scala> it.toStream should contain (2)
    

    We recommend you convert (Scala or Java) iterators to Streams, as shown in the previous example, so that you can continue to reap any potential benefits provided by the laziness of the underlying iterator.

    Inspector shorthands

    You can use the Inspectors syntax with matchers as well as assertions. If you have a multi-dimensional collection, such as a list of lists, using Inspectors is your best option:

    val yss =
      List(
        List(1, 2, 3),
        List(1, 2, 3),
        List(1, 2, 3)
      )
    
    forAll (yss) { ys =>
      forAll (ys) { y => y should be > 0 }
    }
    

    For assertions on one-dimensional collections, however, matchers provides "inspector shorthands." Instead of writing:

    val xs = List(1, 2, 3)
    forAll (xs) { x => x should be < 10 }
    

    You can write:

    all (xs) should be < 10
    

    The previous statement asserts that all elements of the xs list should be less than 10. All of the inspectors have shorthands in matchers. Here is the full list:

    • all - succeeds if the assertion holds true for every element
    • atLeast - succeeds if the assertion holds true for at least the specified number of elements
    • atMost - succeeds if the assertion holds true for at most the specified number of elements
    • between - succeeds if the assertion holds true for between the specified minimum and maximum number of elements, inclusive
    • every - same as all, but lists all failing elements if it fails (whereas all just reports the first failing element)
    • exactly - succeeds if the assertion holds true for exactly the specified number of elements

    Here are some examples:

    scala> import org.scalatest.Matchers._
    import org.scalatest.Matchers._
    
    scala> val xs = List(1, 2, 3, 4, 5)
    xs: List[Int] = List(1, 2, 3, 4, 5)
    
    scala> all (xs) should be > 0
    
    scala> atMost (2, xs) should be >= 4
    
    scala> atLeast (3, xs) should be < 5
    
    scala> between (2, 3, xs) should (be > 1 and be < 5)
    
    scala> exactly (2, xs) should be <= 2
    
    scala> every (xs) should be < 10
    
    scala> // And one that fails...
    
    scala> exactly (2, xs) shouldEqual 2
    org.scalatest.exceptions.TestFailedException: 'exactly(2)' inspection failed, because only 1 element
        satisfied the assertion block at index 1:
      at index 0, 1 did not equal 2,
      at index 2, 3 did not equal 2,
      at index 3, 4 did not equal 2,
      at index 4, 5 did not equal 2
    in List(1, 2, 3, 4, 5)
            at ...
    

    Like Inspectors, objects used with inspector shorthands can be any type T for which a Collecting[T, E] is availabe, which by default includes GenTraversable, Java Collection, Java Map, Arrays, and Strings. Here are some examples:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import Matchers._
    import Matchers._
    
    scala> all (Array(1, 2, 3)) should be < 5
    
    scala> import collection.JavaConverters._
    import collection.JavaConverters._
    
    scala> val js = List(1, 2, 3).asJava
    js: java.util.List[Int] = [1, 2, 3]
    
    scala> all (js) should be < 5
    
    scala> val jmap = Map("a" -> 1, "b" -> 2).asJava
    jmap: java.util.Map[String,Int] = {a=1, b=2}
    
    scala> atLeast(1, jmap) shouldBe Entry("b", 2)
    
    scala> atLeast(2, "hello, world!") shouldBe 'o'
    

    Single-element collections

    To assert both that a collection contains just one "lone" element as well as something else about that element, you can use the loneElement syntax provided by trait LoneElement. For example, if a Set[Int] should contain just one element, an Int less than or equal to 10, you could write:

    import LoneElement._
    set.loneElement should be <= 10
    

    You can invoke loneElement on any type T for which an implicit Collecting[E, T] is available, where E is the element type returned by the loneElement invocation. By default, you can use loneElement on GenTraversable, Java Collection, Java Map, Array, and String.

    Java collections and maps

    You can use similar syntax on Java collections (java.util.Collection) and maps (java.util.Map). For example, you can check whether a Java Collection or Map is empty, like this:

    javaCollection should be ('empty)
    javaMap should be ('empty)
    

    Even though Java's List type doesn't actually have a length or getLength method, you can nevertheless check the length of a Java List (java.util.List) like this:

    javaList should have length 9
    

    You can check the size of any Java Collection or Map, like this:

    javaMap should have size 20
    javaSet should have size 90
    

    In addition, you can check whether a Java Collection contains a particular element, like this:

    javaCollection should contain ("five")
    

    One difference to note between the syntax supported on Java and Scala collections is that in Java, Map is not a subtype of Collection, and does not actually define an element type. You can ask a Java Map for an "entry set" via the entrySet method, which will return the Map's key/value pairs wrapped in a set of java.util.Map.Entry, but a Map is not actually a collection of Entry. To make Java Maps easier to work with, however, ScalaTest matchers allows you to treat a Java Map as a collection of Entry, and defines a convenience implementation of java.util.Map.Entry in org.scalatest.Entry. Here's how you use it:

    javaMap should contain (Entry(2, 3))
    javaMap should contain oneOf (Entry(2, 3), Entry(3, 4))
    

    You can you alse just check whether a Java Map contains a particular key, or value, like this:

    javaMap should contain key 1
    javaMap should contain value "Howdy"
    

    Strings and Arrays as collections

    You can also use all the syntax described above for Scala and Java collections on Arrays and Strings. Here are some examples:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import Matchers._
    import Matchers._
    
    scala> atLeast (2, Array(1, 2, 3)) should be > 1
    
    scala> atMost (2, "halloo") shouldBe 'o'
    
    scala> Array(1, 2, 3) shouldBe sorted
    
    scala> "abcdefg" shouldBe sorted
    
    scala> Array(1, 2, 3) should contain atMostOneOf (3, 4, 5)
    
    scala> "abc" should contain atMostOneOf ('c', 'd', 'e')
    

    be as an equality comparison

    All uses of be other than those shown previously perform an equality comparison. They work the same as equal when it is used with default equality. This redundancy between be and equals exists in part because it enables syntax that sometimes sounds more natural. For example, instead of writing:

    result should equal (null)
    

    You can write:

    result should be (null)
    

    (Hopefully you won't write that too much given null is error prone, and Option is usually a better, well, option.) As mentioned previously, the other difference between equal and be is that equal delegates the equality check to an Equality typeclass, whereas be always uses default equality. Here are some other examples of be used for equality comparison:

    sum should be (7.0)
    boring should be (false)
    fun should be (true)
    list should be (Nil)
    option should be (None)
    option should be (Some(1))
    

    As with equal used with default equality, using be on arrays results in deep being called on both arrays prior to calling equal. As a result, the following expression would not throw a TestFailedException:

    Array(1, 2) should be (Array(1, 2)) // succeeds (i.e., does not throw TestFailedException)
    

    Because be is used in several ways in ScalaTest matcher syntax, just as it is used in many ways in English, one potential point of confusion in the event of a failure is determining whether be was being used as an equality comparison or in some other way, such as a property assertion. To make it more obvious when be is being used for equality, the failure messages generated for those equality checks will include the word equal in them. For example, if this expression fails with a TestFailedException:

    option should be (Some(1))
    

    The detail message in that TestFailedException will include the words "equal to" to signify be was in this case being used for equality comparison:

    Some(2) was not equal to Some(1)
    

    Being negative

    If you wish to check the opposite of some condition, you can simply insert not in the expression. Here are a few examples:

    result should not be (null)
    sum should not be <= (10)
    mylist should not equal (yourList)
    string should not startWith ("Hello")
    

    Checking that a snippet of code does not compile

    Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest Matchers trait includes the following syntax for that purpose:

    "val a: String = 1" shouldNot compile
    

    If you want to ensure that a snippet of code does not compile because of a type error (as opposed to a syntax error), use:

    "val a: String = 1" shouldNot typeCheck
    

    Note that the shouldNot typeCheck syntax will only succeed if the given snippet of code does not compile because of a type error. A syntax error will still result on a thrown TestFailedException.

    If you want to state that a snippet of code does compile, you can make that more obvious with:

    "val a: Int = 1" should compile
    

    Although the previous three constructs are implemented with macros that determine at compile time whether the snippet of code represented by the string does or does not compile, errors are reported as test failures at runtime.

    Logical expressions with and and or

    You can also combine matcher expressions with and and/or or, however, you must place parentheses or curly braces around the and or or expression. For example, this and-expression would not compile, because the parentheses are missing:

    map should contain key ("two") and not contain value (7) // ERROR, parentheses missing!
    

    Instead, you need to write:

    map should (contain key ("two") and not contain value (7))
    

    Here are some more examples:

    number should (be > (0) and be <= (10))
    option should (equal (Some(List(1, 2, 3))) or be (None))
    string should (
      equal ("fee") or
      equal ("fie") or
      equal ("foe") or
      equal ("fum")
    )
    

    Two differences exist between expressions composed of these and and or operators and the expressions you can write on regular Booleans using its && and || operators. First, expressions with and and or do not short-circuit. The following contrived expression, for example, would print "hello, world!":

    "yellow" should (equal ("blue") and equal { println("hello, world!"); "green" })
    

    In other words, the entire and or or expression is always evaluated, so you'll see any side effects of the right-hand side even if evaluating only the left-hand side is enough to determine the ultimate result of the larger expression. Failure messages produced by these expressions will "short-circuit," however, mentioning only the left-hand side if that's enough to determine the result of the entire expression. This "short-circuiting" behavior of failure messages is intended to make it easier and quicker for you to ascertain which part of the expression caused the failure. The failure message for the previous expression, for example, would be:

    "yellow" did not equal "blue"
    

    Most likely this lack of short-circuiting would rarely be noticeable, because evaluating the right hand side will usually not involve a side effect. One situation where it might show up, however, is if you attempt to and a null check on a variable with an expression that uses the variable, like this:

    map should (not be (null) and contain key ("ouch"))
    

    If map is null, the test will indeed fail, but with a NullArgumentException, not a TestFailedException. Here, the NullArgumentException is the visible right-hand side effect. To get a TestFailedException, you would need to check each assertion separately:

    map should not be (null)
    map should contain key ("ouch")
    

    If map is null in this case, the null check in the first expression will fail with a TestFailedException, and the second expression will never be executed.

    The other difference with Boolean operators is that although && has a higher precedence than ||, and and or have the same precedence. Thus although the Boolean expression (a || b && c) will evaluate the && expression before the || expression, like (a || (b && c)), the following expression:

    traversable should (contain (7) or contain (8) and have size (9))
    

    Will evaluate left to right, as:

    traversable should ((contain (7) or contain (8)) and have size (9))
    

    If you really want the and part to be evaluated first, you'll need to put in parentheses, like this:

    traversable should (contain (7) or (contain (8) and have size (9)))
    

    Working with Options

    You can work with options using ScalaTest's equality, empty, defined, and contain syntax. For example, if you wish to check whether an option is None, you can write any of:

    option shouldEqual None
    option shouldBe None
    option should === (None)
    option shouldBe empty
    

    If you wish to check an option is defined, and holds a specific value, you can write any of:

    option shouldEqual Some("hi")
    option shouldBe Some("hi")
    option should === (Some("hi"))
    

    If you only wish to check that an option is defined, but don't care what it's value is, you can write:

    option shouldBe defined
    

    If you mix in (or import the members of) OptionValues, you can write one statement that indicates you believe an option should be defined and then say something else about its value. Here's an example:

    import org.scalatest.OptionValues._
    option.value should be < 7
    

    As mentioned previously, you can use also use ScalaTest's contain, contain oneOf, and contain noneOf syntax with options:

    Some(2) should contain (2)
    Some(7) should contain oneOf (5, 7, 9)
    Some(0) should contain noneOf (7, 8, 9)
    

    Checking arbitrary properties with have

    Using have, you can check properties of any type, where a property is an attribute of any object that can be retrieved either by a public field, method, or JavaBean-style get or is method, like this:

    book should have (
      'title ("Programming in Scala"),
      'author (List("Odersky", "Spoon", "Venners")),
      'pubYear (2008)
    )
    

    This expression will use reflection to ensure the title, author, and pubYear properties of object book are equal to the specified values. For example, it will ensure that book has either a public Java field or method named title, or a public method named getTitle, that when invoked (or accessed in the field case) results in a the string "Programming in Scala". If all specified properties exist and have their expected values, respectively, execution will continue. If one or more of the properties either does not exist, or exists but results in an unexpected value, a TestFailedException will be thrown that explains the problem. (For the details on how a field or method is selected during this process, see the documentation for HavePropertyMatcherGenerator.)

    When you use this syntax, you must place one or more property values in parentheses after have, seperated by commas, where a property value is a symbol indicating the name of the property followed by the expected value in parentheses. The only exceptions to this rule is the syntax for checking size and length shown previously, which does not require parentheses. If you forget and put parentheses in, however, everything will still work as you'd expect. Thus instead of writing:

    array should have length (3)
    set should have size (90)
    

    You can alternatively, write:

    array should have (length (3))
    set should have (size (90))
    

    If a property has a value different from the specified expected value, a TestFailedError will be thrown with a detailed message that explains the problem. For example, if you assert the following on a book whose title is Moby Dick:

    book should have ('title ("A Tale of Two Cities"))
    

    You'll get a TestFailedException with this detail message:

    The title property had value "Moby Dick", instead of its expected value "A Tale of Two Cities",
    on object Book("Moby Dick", "Melville", 1851)
    

    If you prefer to check properties in a type-safe manner, you can use a HavePropertyMatcher. This would allow you to write expressions such as:

    book should have (
      title ("Programming in Scala"),
      author (List("Odersky", "Spoon", "Venners")),
      pubYear (2008)
    )
    

    These expressions would fail to compile if should is used on an inappropriate type, as determined by the type parameter of the HavePropertyMatcher being used. (For example, title in this example might be of type HavePropertyMatcher[org.publiclibrary.Book]. If used with an appropriate type, such an expression will compile and at run time the property method or field will be accessed directly; i.e., no reflection will be used. See the documentation for HavePropertyMatcher for more information.

    Using length and size with HavePropertyMatchers

    If you want to use length or size syntax with your own custom HavePropertyMatchers, you can do so, but you must write (of [“the type”]) afterwords. For example, you could write:

    book should have (
      title ("A Tale of Two Cities"),
      length (220) (of [Book]),
      author ("Dickens")
    )
    

    Prior to ScalaTest 2.0, “length (22)” yielded a HavePropertyMatcher[Any, Int] that used reflection to dynamically look for a length field or getLength method. In ScalaTest 2.0, “length (22)” yields a MatcherFactory1[Any, Length], so it is no longer a HavePropertyMatcher. The (of [<type>]) syntax converts the the MatcherFactory1[Any, Length] to a HavePropertyMatcher[<type>, Int].

    Checking that an expression matches a pattern

    ScalaTest's Inside trait allows you to make assertions after a pattern match. Here's an example:

    case class Name(first: String, middle: String, last: String)
    
    val name = Name("Jane", "Q", "Programmer")
    
    inside(name) { case Name(first, _, _) =>
      first should startWith ("S")
    }
    

    You can use inside to just ensure a pattern is matched, without making any further assertions, but a better alternative for that kind of assertion is matchPattern. The matchPattern syntax allows you to express that you expect a value to match a particular pattern, no more and no less:

    name should matchPattern { case Name("Sarah", _, _) => }
    

    Using custom matchers

    If none of the built-in matcher syntax (or options shown so far for extending the syntax) satisfy a particular need you have, you can create custom Matchers that allow you to place your own syntax directly after should. For example, class java.io.File has a method isHidden, which indicates whether a file of a certain path and name is hidden. Because the isHidden method takes no parameters and returns Boolean, you can call it using be with a symbol or BePropertyMatcher, yielding assertions like:

    file should be ('hidden)  // using a symbol
    file should be (hidden)   // using a BePropertyMatcher
    

    If it doesn't make sense to have your custom syntax follow be, you might want to create a custom Matcher instead, so your syntax can follow should directly. For example, you might want to be able to check whether a java.io.File's name ends with a particular extension, like this:

    // using a plain-old Matcher
    file should endWithExtension ("txt")
    

    ScalaTest provides several mechanism to make it easy to create custom matchers, including ways to compose new matchers out of existing ones complete with new error messages. For more information about how to create custom Matchers, please see the documentation for the Matcher trait.

    Checking for expected exceptions

    Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. With Matchers mixed in, you can check for an expected exception like this:

    an [IndexOutOfBoundsException] should be thrownBy s.charAt(-1)
    

    If charAt throws an instance of StringIndexOutOfBoundsException, this expression will result in that exception. But if charAt completes normally, or throws a different exception, this expression will complete abruptly with a TestFailedException.

    If you need to further isnpect an expected exception, you can capture it using this syntax:

    val thrown = the [IndexOutOfBoundsException] thrownBy s.charAt(-1)
    

    This expression returns the caught exception so that you can inspect it further if you wish, for example, to ensure that data contained inside the exception has the expected values. Here's an example:

    thrown.getMessage should equal ("String index out of range: -1")
    

    If you prefer you can also capture and inspect an expected exception in one statement, like this:

    the [ArithmeticException] thrownBy 1 / 0 should have message "/ by zero"
    the [IndexOutOfBoundsException] thrownBy {
      s.charAt(-1)
    } should have message "String index out of range: -1"
    

    You can also state that no exception should be thrown by some code, like this:

    noException should be thrownBy 0 / 1
    

    Those pesky parens

    Perhaps the most tricky part of writing assertions using ScalaTest matchers is remembering when you need or don't need parentheses, but bearing in mind a few simple rules should help. It is also reassuring to know that if you ever leave off a set of parentheses when they are required, your code will not compile. Thus the compiler will help you remember when you need the parens. That said, the rules are:

    1. Although you don't always need them, you may choose to always put parentheses around right-hand values, such as the 7 in num should equal (7):

    result should equal (4)
    array should have length (3)
    book should have (
      'title ("Programming in Scala"),
      'author (List("Odersky", "Spoon", "Venners")),
      'pubYear (2008)
    )
    option should be ('defined)
    catMap should (contain key (9) and contain value ("lives"))
    keyEvent should be an ('actionKey)
    javaSet should have size (90)
    

    2. Except for length, size and message, you must always put parentheses around the list of one or more property values following a have:

    file should (exist and have ('name ("temp.txt")))
    book should have (
      title ("Programming in Scala"),
      author (List("Odersky", "Spoon", "Venners")),
      pubYear (2008)
    )
    javaList should have length (9) // parens optional for length and size
    

    3. You must always put parentheses around and and or expressions, as in:

    catMap should (contain key (9) and contain value ("lives"))
    number should (equal (2) or equal (4) or equal (8))
    

    4. Although you don't always need them, you may choose to always put parentheses around custom Matchers when they appear directly after not:

    file should exist
    file should not (exist)
    file should (exist and have ('name ("temp.txt")))
    file should (not (exist) and have ('name ("temp.txt"))
    file should (have ('name ("temp.txt") or exist)
    file should (have ('name ("temp.txt") or not (exist))
    

    That's it. With a bit of practice it should become natural to you, and the compiler will always be there to tell you if you forget a set of needed parentheses.

    Note: ScalaTest's matchers are in part inspired by the matchers of RSpec, Hamcrest, and specs2, and its “shouldNot compile” syntax by the illTyped macro of shapeless.

  68. trait MustMatchers extends Assertions with Tolerance with MustVerb with MatcherWords with Explicitly

    Permalink

    Trait that provides a domain specific language (DSL) for expressing assertions in tests using the word must.

    Trait that provides a domain specific language (DSL) for expressing assertions in tests using the word must.

    For example, if you mix Matchers into a suite class, you can write an equality assertion in that suite like this:

    result must equal (3)
    

    Here result is a variable, and can be of any type. If the object is an Int with the value 3, execution will continue (i.e., the expression will result in the unit value, ()). Otherwise, a TestFailedException will be thrown with a detail message that explains the problem, such as "7 did not equal 3". This TestFailedException will cause the test to fail.

    Here is a table of contents for this documentation:

    Trait MustMatchers is an alternative to Matchers that provides the exact same meaning, syntax, and behavior as Matchers, but uses the verb must instead of should. The two traits differ only in the English semantics of the verb: should is informal, making the code feel like conversation between the writer and the reader; must is more formal, making the code feel more like a written specification.

    Checking equality with matchers

    ScalaTest matchers provides five different ways to check equality, each designed to address a different need. They are:

    result must equal (3) // can customize equality
    result must === (3)   // can customize equality and enforce type constraints
    result must be (3)    // cannot customize equality, so fastest to compile
    result mustEqual 3    // can customize equality, no parentheses required
    result mustBe 3       // cannot customize equality, so fastest to compile, no parentheses required
    

    The “left must equal (right)” syntax requires an org.scalactic.Equality[L] to be provided (either implicitly or explicitly), where L is the left-hand type on which must is invoked. In the "left must equal (right)" case, for example, L is the type of left. Thus if left is type Int, the "left must equal (right)" statement would require an Equality[Int].

    By default, an implicit Equality[T] instance is available for any type T, in which equality is implemented by simply invoking == on the left value, passing in the right value, with special treatment for arrays. If either left or right is an array, deep will be invoked on it before comparing with ==. Thus, the following expression will yield false, because Array's equals method compares object identity:

    Array(1, 2) == Array(1, 2) // yields false
    

    The next expression will by default not result in a TestFailedException, because default Equality[Array[Int]] compares the two arrays structurally, taking into consideration the equality of the array's contents:

    Array(1, 2) must equal (Array(1, 2)) // succeeds (i.e., does not throw TestFailedException)
    

    If you ever do want to verify that two arrays are actually the same object (have the same identity), you can use the be theSameInstanceAs syntax, described below.

    You can customize the meaning of equality for a type when using "must equal," "must ===," or mustEqual syntax by defining implicit Equality instances that will be used instead of default Equality. You might do this to normalize types before comparing them with ==, for instance, or to avoid calling the == method entirely, such as if you want to compare Doubles with a tolerance. For an example, see the main documentation of trait Equality.

    You can always supply implicit parameters explicitly, but in the case of implicit parameters of type Equality[T], Scalactic provides a simple "explictly" DSL. For example, here's how you could explicitly supply an Equality[String] instance that normalizes both left and right sides (which must be strings), by transforming them to lowercase:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> import org.scalactic.Explicitly._
    import org.scalactic.Explicitly._
    
    scala> import org.scalactic.StringNormalizations._
    import org.scalactic.StringNormalizations._
    
    scala> "Hi" must equal ("hi") (after being lowerCased)
    

    The after being lowerCased expression results in an Equality[String], which is then passed explicitly as the second curried parameter to equal. For more information on the explictly DSL, see the main documentation for trait Explicitly.

    The "must be" and mustBe syntax do not take an Equality[T] and can therefore not be customized. They always use the default approach to equality described above. As a result, "must be" and mustBe will likely be the fastest-compiling matcher syntax for equality comparisons, since the compiler need not search for an implicit Equality[T] each time.

    The must === syntax (and its complement, must !==) can be used to enforce type constraints at compile-time between the left and right sides of the equality comparison. Here's an example:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> import org.scalactic.TypeCheckedTripleEquals._
    import org.scalactic.TypeCheckedTripleEquals._
    
    scala> Some(2) must === (2)
    <console>:17: error: types Some[Int] and Int do not adhere to the equality constraint
    selected for the === and !== operators; the missing implicit parameter is of
    type org.scalactic.CanEqual[Some[Int],Int]
                  Some(2) must === (2)
                          ^
    

    By default, the "Some(2) must === (2)" statement would fail at runtime. By mixing in the equality constraints provided by TypeCheckedTripleEquals, however, the statement fails to compile. For more information and examples, see the main documentation for trait TypeCheckedTripleEquals.

    Checking size and length

    You can check the size or length of any type of object for which it makes sense. Here's how checking for length looks:

    result must have length 3
    

    Size is similar:

    result must have size 10
    

    The length syntax can be used with String, Array, any scala.collection.GenSeq, any java.util.List, and any type T for which an implicit Length[T] type class is available in scope. Similarly, the size syntax can be used with Array, any scala.collection.GenTraversable, any java.util.Collection, any java.util.Map, and any type T for which an implicit Size[T] type class is available in scope. You can enable the length or size syntax for your own arbitrary types, therefore, by defining Length or Size type classes for those types.

    In addition, the length syntax can be used with any object that has a field or method named length or a method named getLength. Similarly, the size syntax can be used with any object that has a field or method named size or a method named getSize. The type of a length or size field, or return type of a method, must be either Int or Long. Any such method must take no parameters. (The Scala compiler will ensure at compile time that the object on which must is being invoked has the appropriate structure.)

    Checking strings

    You can check for whether a string starts with, ends with, or includes a substring like this:

    string must startWith ("Hello")
    string must endWith ("world")
    string must include ("seven")
    

    You can check for whether a string starts with, ends with, or includes a regular expression, like this:

    string must startWith regex "Hel*o"
    string must endWith regex "wo.ld"
    string must include regex "wo.ld"
    

    And you can check whether a string fully matches a regular expression, like this:

    string must fullyMatch regex """(-)?(\d+)(\.\d*)?"""
    

    The regular expression passed following the regex token can be either a String or a scala.util.matching.Regex.

    With the startWith, endWith, include, and fullyMatch tokens can also be used with an optional specification of required groups, like this:

    "abbccxxx" must startWith regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "xxxabbcc" must endWith regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "xxxabbccxxx" must include regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    "abbcc" must fullyMatch regex ("a(b*)(c*)" withGroups ("bb", "cc"))
    

    You can check whether a string is empty with empty:

    s mustBe empty
    

    You can also use most of ScalaTest's matcher syntax for collections on String by treating the Strings as collections of characters. For examples, see the Strings and Arrays as collections section below.

    Greater and less than

    You can check whether any type for which an implicit Ordering[T] is available is greater than, less than, greater than or equal, or less than or equal to a value of type T. The syntax is:

    one must be < 7
    one must be > 0
    one must be <= 7
    one must be >= 0
    

    Checking Boolean properties with be

    If an object has a method that takes no parameters and returns boolean, you can check it by placing a Symbol (after be) that specifies the name of the method (excluding an optional prefix of "is"). A symbol literal in Scala begins with a tick mark and ends at the first non-identifier character. Thus, 'traversableAgain results in a Symbol object at runtime, as does 'completed and 'file. Here's an example:

    iter mustBe 'traversableAgain
    

    Given this code, ScalaTest will use reflection to look on the object referenced from emptySet for a method that takes no parameters and results in Boolean, with either the name empty or isEmpty. If found, it will invoke that method. If the method returns true, execution will continue. But if it returns false, a TestFailedException will be thrown that will contain a detail message, such as:

    non-empty iterator was not traversableAgain
    

    This be syntax can be used with any reference (AnyRef) type. If the object does not have an appropriately named predicate method, you'll get a TestFailedException at runtime with a detailed message that explains the problem. (For the details on how a field or method is selected during this process, see the documentation for BeWord.)

    If you think it reads better, you can optionally put a or an after be. For example, java.io.File has two predicate methods, isFile and isDirectory. Thus with a File object named temp, you could write:

    temp must be a 'file
    

    Or, given java.awt.event.KeyEvent has a method isActionKey that takes no arguments and returns Boolean, you could assert that a KeyEvent is an action key with:

    keyEvent must be an 'actionKey
    

    If you prefer to check Boolean properties in a type-safe manner, you can use a BePropertyMatcher. This would allow you to write expressions such as:

    xs mustBe traversableAgain
    temp must be a file
    keyEvent must be an actionKey
    

    These expressions would fail to compile if must is used on an inappropriate type, as determined by the type parameter of the BePropertyMatcher being used. (For example, file in this example would likely be of type BePropertyMatcher[java.io.File]. If used with an appropriate type, such an expression will compile and at run time the Boolean property method or field will be accessed directly; i.e., no reflection will be used. See the documentation for BePropertyMatcher for more information.

    Using custom BeMatchers

    If you want to create a new way of using be, which doesn't map to an actual property on the type you care about, you can create a BeMatcher. You could use this, for example, to create BeMatcher[Int] called odd, which would match any odd Int, and even, which would match any even Int. Given this pair of BeMatchers, you could check whether an Int was odd or even with expressions like:

    num mustBe odd
    num must not be even
    

    For more information, see the documentation for BeMatcher.

    Checking object identity

    If you need to check that two references refer to the exact same object, you can write:

    ref1 must be theSameInstanceAs ref2
    

    Checking an object's class

    If you need to check that an object is an instance of a particular class or trait, you can supply the type to “be a” or “be an”:

    result1 mustBe a [Tiger]
    result1 must not be an [Orangutan]
    

    Because type parameters are erased on the JVM, we recommend you insert an underscore for any type parameters when using this syntax. Both of the following test only that the result is an instance of List[_], because at runtime the type parameter has been erased:

    result mustBe a [List[_]] // recommended
    result mustBe a [List[Fruit]] // discouraged
    

    Checking numbers against a range

    Often you may want to check whether a number is within a range. You can do that using the +- operator, like this:

    sevenDotOh must equal (6.9 +- 0.2)
    sevenDotOh must === (6.9 +- 0.2)
    sevenDotOh must be (6.9 +- 0.2)
    sevenDotOh mustEqual 6.9 +- 0.2
    sevenDotOh mustBe 6.9 +- 0.2
    

    Any of these expressions will cause a TestFailedException to be thrown if the floating point value, sevenDotOh is outside the range 6.7 to 7.1. You can use +- with any type T for which an implicit Numeric[T] exists, such as integral types:

    seven must equal (6 +- 2)
    seven must === (6 +- 2)
    seven must be (6 +- 2)
    seven mustEqual 6 +- 2
    seven mustBe 6 +- 2
    

    Checking for emptiness

    You can check whether an object is "empty", like this:

    traversable mustBe empty
    javaMap must not be empty
    

    The empty token can be used with any type L for which an implicit Emptiness[L] exists. The Emptiness companion object provides implicits for GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E], and Option[E]. In addition, the Emptiness companion object provides structural implicits for types that declare an isEmpty method that returns a Boolean. Here are some examples:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> List.empty mustBe empty
    
    scala> None mustBe empty
    
    scala> Some(1) must not be empty
    
    scala> "" mustBe empty
    
    scala> new java.util.HashMap[Int, Int] mustBe empty
    
    scala> new { def isEmpty = true} mustBe empty
    
    scala> Array(1, 2, 3) must not be empty
    

    Working with "containers"

    You can check whether a collection contains a particular element like this:

    traversable must contain ("five")
    

    The contain syntax shown above can be used with any type C that has a "containing" nature, evidenced by an implicit org.scalatest.enablers.Containing[L], where L is left-hand type on which must is invoked. In the Containing companion object, implicits are provided for types GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E], and Option[E]. Here are some examples:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> List(1, 2, 3) must contain (2)
    
    scala> Map('a' -> 1, 'b' -> 2, 'c' -> 3) must contain ('b' -> 2)
    
    scala> Set(1, 2, 3) must contain (2)
    
    scala> Array(1, 2, 3) must contain (2)
    
    scala> "123" must contain ('2')
    
    scala> Some(2) must contain (2)
    

    ScalaTest's implicit methods that provide the Containing[L] type classes require an Equality[E], where E is an element type. For example, to obtain a Containing[Array[Int]] you must supply an Equality[Int], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Containing[L], implicit conversions are provided in the Containing companion object from Equality[E] to the various types of containers of E. Here's an example:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> List("Hi", "Di", "Ho") must contain ("ho")
    org.scalatest.exceptions.TestFailedException: List(Hi, Di, Ho) did not contain element "ho"
            at ...
    
    scala> import org.scalactic.Explicitly._
    import org.scalactic.Explicitly._
    
    scala> import org.scalactic.StringNormalizations._
    import org.scalactic.StringNormalizations._
    
    scala> (List("Hi", "Di", "Ho") must contain ("ho")) (after being lowerCased)
    

    Note that when you use the explicitly DSL with contain you need to wrap the entire contain expression in parentheses, as shown here.

    (List("Hi", "Di", "Ho") must contain ("ho")) (after being lowerCased)
    ^                                            ^
    

    In addition to determining whether an object contains another object, you can use contain to make other determinations. For example, the contain oneOf syntax ensures that one and only one of the specified elements are contained in the containing object:

    List(1, 2, 3, 4, 5) must contain oneOf (5, 7, 9)
    Some(7) must contain oneOf (5, 7, 9)
    "howdy" must contain oneOf ('a', 'b', 'c', 'd')
    

    Note that if multiple specified elements appear in the containing object, oneOf will fail:

    scala> List(1, 2, 3) must contain oneOf (2, 3, 4)
    org.scalatest.exceptions.TestFailedException: List(1, 2, 3) did not contain one (and only one) of (2, 3, 4)
            at ...
    

    If you really want to ensure one or more of the specified elements are contained in the containing object, use atLeastOneOf, described below, instead of oneOf. Keep in mind, oneOf means "exactly one of."

    Note also that with any contain syntax, you can place custom implicit Equality[E] instances in scope to customize how containership is determined, or use the explicitly DSL. Here's an example:

    (Array("Doe", "Ray", "Me") must contain oneOf ("X", "RAY", "BEAM")) (after being lowerCased)
    

    If you have a collection of elements that you'd like to use in a "one of" comparison, you can use "oneElementOf," like this:

    List(1, 2, 3, 4, 5) must contain oneElementOf List(5, 7, 9)
    Some(7) must contain oneElementOf Vector(5, 7, 9)
    "howdy" must contain oneElementOf Set('a', 'b', 'c', 'd')
    (Array("Doe", "Ray", "Me") must contain oneElementOf List("X", "RAY", "BEAM")) (after being lowerCased)
    

    The contain noneOf syntax does the opposite of oneOf: it ensures none of the specified elements are contained in the containing object:

    List(1, 2, 3, 4, 5) must contain noneOf (7, 8, 9)
    Some(0) must contain noneOf (7, 8, 9)
    "12345" must contain noneOf ('7', '8', '9')
    

    If you have a collection of elements that you'd like to use in a "none of" comparison, you can use "noElementsOf," like this:

    List(1, 2, 3, 4, 5) must contain noElementsOf List(7, 8, 9)
    Some(0) must contain noElementsOf Vector(7, 8, 9)
    "12345" must contain noElementsOf Set('7', '8', '9')
    

    Working with "aggregations"

    As mentioned, the "contain," "contain oneOf," and "contain noneOf" syntax requires a Containing[L] be provided, where L is the left-hand type. Other contain syntax, which will be described in this section, requires an Aggregating[L] be provided, where again L is the left-hand type. (An Aggregating[L] instance defines the "aggregating nature" of a type L.) The reason, essentially, is that contain syntax that makes sense for Option is enabled by Containing[L], whereas syntax that does not make sense for Option is enabled by Aggregating[L]. For example, it doesn't make sense to assert that an Option[Int] contains all of a set of integers, as it could only ever contain one of them. But this does make sense for a type such as List[Int] that can aggregate zero to many integers.

    The Aggregating companion object provides implicit instances of Aggregating[L] for types GenTraversable[E], java.util.Collection[E], java.util.Map[K, V], String, Array[E]. Note that these are the same types as are supported with Containing, but with Option[E] missing. Here are some examples:

    The contain atLeastOneOf syntax, for example, works for any type L for which an Aggregating[L] exists. It ensures that at least one of (i.e., one or more of) the specified objects are contained in the containing object:

    List(1, 2, 3) must contain atLeastOneOf (2, 3, 4)
    Array(1, 2, 3) must contain atLeastOneOf (3, 4, 5)
    "abc" must contain atLeastOneOf ('c', 'a', 't')
    

    Similar to Containing[L], the implicit methods that provide the Aggregating[L] instances require an Equality[E], where E is an element type. For example, to obtain a Aggregating[Vector[String]] you must supply an Equality[String], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Aggregating[L], implicit conversions are provided in the Aggregating companion object from Equality[E] to the various types of aggregations of E. Here's an example:

    (Vector(" A", "B ") must contain atLeastOneOf ("a ", "b", "c")) (after being lowerCased and trimmed)
    

    If you have a collection of elements that you'd like to use in an "at least one of" comparison, you can use "atLeastOneElementOf," like this:

    List(1, 2, 3) must contain atLeastOneElementOf List(2, 3, 4)
    Array(1, 2, 3) must contain atLeastOneElementOf Vector(3, 4, 5)
    "abc" must contain atLeastOneElementOf Set('c', 'a', 't')
    (Vector(" A", "B ") must contain atLeastOneElementOf List("a ", "b", "c")) (after being lowerCased and trimmed)
    

    The "contain atMostOneOf" syntax lets you specify a set of objects at most one of which must be contained in the containing object:

    List(1, 2, 3, 4, 5) must contain atMostOneOf (5, 6, 7)
    

    If you have a collection of elements that you'd like to use in a "at most one of" comparison, you can use "atMostOneElementOf," like this:

    List(1, 2, 3, 4, 5) must contain atMostOneElementOf Vector(5, 6, 7)
    

    The "contain allOf" syntax lets you specify a set of objects that must all be contained in the containing object:

    List(1, 2, 3, 4, 5) must contain allOf (2, 3, 5)
    

    If you have a collection of elements that you'd like to use in a "all of" comparison, you can use "allElementsOf," like this:

    List(1, 2, 3, 4, 5) must contain allElementsOf Array(2, 3, 5)
    

    The "contain only" syntax lets you assert that the containing object contains only the specified objects, though it may contain more than one of each:

    List(1, 2, 3, 2, 1) must contain only (1, 2, 3)
    

    The "contain theSameElementsAs" and "contain theSameElementsInOrderAs syntax differ from the others in that the right hand side is a GenTraversable[_] rather than a varargs of Any. (Note: in a future 2.0 milestone release, possibly 2.0.M6, these will likely be widened to accept any type R for which an Aggregating[R] exists.)

    The "contain theSameElementsAs" syntax lets you assert that two aggregations contain the same objects:

    List(1, 2, 2, 3, 3, 3) must contain theSameElementsAs Vector(3, 2, 3, 1, 2, 3)
    

    The number of times any family of equal objects appears must also be the same in both the left and right aggregations. The specified objects may appear multiple times, but must appear in the order they appear in the right-hand list. For example, if the last 3 element is left out of the right-hand list in the previous example, the expression would fail because the left side has three 3's and the right hand side has only two:

    List(1, 2, 2, 3, 3, 3) must contain theSameElementsAs Vector(3, 2, 3, 1, 2)
    org.scalatest.exceptions.TestFailedException: List(1, 2, 2, 3, 3, 3) did not contain the same elements as Vector(3, 2, 3, 1, 2)
            at ...
    

    Note that no onlyElementsOf matcher is provided, because it would have the same behavior as theSameElementsAs. (I.e., if you were looking for onlyElementsOf, please use theSameElementsAs instead.)

    Working with "sequences"

    The rest of the contain syntax, which will be described in this section, requires a Sequencing[L] be provided, where again L is the left-hand type. (A Sequencing[L] instance defines the "sequencing nature" of a type L.) The reason, essentially, is that contain syntax that implies an "order" of elements makes sense only for types that place elements in a sequence. For example, it doesn't make sense to assert that a Map[String, Int] or Set[Int] contains all of a set of integers in a particular order, as these types don't necessarily define an order for their elements. But this does make sense for a type such as Seq[Int] that does define an order for its elements.

    The Sequencing companion object provides implicit instances of Sequencing[L] for types GenSeq[E], java.util.List[E], String, and Array[E]. Here are some examples:

    Similar to Containing[L], the implicit methods that provide the Aggregating[L] instances require an Equality[E], where E is an element type. For example, to obtain a Aggregating[Vector[String]] you must supply an Equality[String], either implicitly or explicitly. The contain syntax uses this Equality[E] to determine containership. Thus if you want to change how containership is determined for an element type E, place an implicit Equality[E] in scope or use the explicitly DSL. Although the implicit parameter required for the contain syntax is of type Aggregating[L], implicit conversions are provided in the Aggregating companion object from Equality[E] to the various types of aggregations of E. Here's an example:

    The "contain inOrderOnly" syntax lets you assert that the containing object contains only the specified objects, in order. The specified objects may appear multiple times, but must appear in the order they appear in the right-hand list. Here's an example:

    List(1, 2, 2, 3, 3, 3) must contain inOrderOnly (1, 2, 3)
    

    The "contain inOrder" syntax lets you assert that the containing object contains only the specified objects in order, like inOrderOnly, but allows other objects to appear in the left-hand aggregation as well: contain more than one of each:

    List(0, 1, 2, 2, 99, 3, 3, 3, 5) must contain inOrder (1, 2, 3)
    

    If you have a collection of elements that you'd like to use in a "in order" comparison, you can use "inOrderElementsOf," like this:

    List(0, 1, 2, 2, 99, 3, 3, 3, 5) must contain inOrderElementsOf Array(1, 2, 3)
    

    Note that "order" in inOrder, inOrderOnly, and theSameElementsInOrderAs (described below) in the Aggregation[L] instances built-in to ScalaTest is defined as "iteration order".

    Lastly, the "contain theSameElementsInOrderAs" syntax lets you assert that two aggregations contain the same exact elements in the same (iteration) order:

    List(1, 2, 3) must contain theSameElementsInOrderAs collection.mutable.TreeSet(3, 2, 1)
    

    The previous assertion succeeds because the iteration order of aTreeSet is the natural ordering of its elements, which in this case is 1, 2, 3. An iterator obtained from the left-hand List will produce the same elements in the same order.

    Note that no inOrderOnlyElementsOf matcher is provided, because it would have the same behavior as theSameElementsInOrderAs. (I.e., if you were looking for inOrderOnlyElementsOf, please use theSameElementsInOrderAs instead.)

    Working with "sortables"

    You can also ask whether the elements of "sortable" objects (such as Arrays, Java Lists, and GenSeqs) are in sorted order, like this:

    List(1, 2, 3) mustBe sorted
    

    Working with iterators

    Althought it seems desireable to provide similar matcher syntax for Scala and Java iterators to that provided for sequences like Seqs, Array, and java.util.List, the ephemeral nature of iterators makes this problematic. Some syntax (such as must contain) is relatively straightforward to support on iterators, but other syntax (such as, for example, Inspector expressions on nested iterators) is not. Rather than allowing inconsistencies between sequences and iterators in the API, we chose to not support any such syntax directly on iterators:

    scala> val it = List(1, 2, 3).iterator
    it: Iterator[Int] = non-empty iterator
    
    scala> it must contain (2)
    <console>:15: error: could not find implicit value for parameter typeClass1: org.scalatest.enablers.Containing[Iterator[Int]]
               it must contain (2)
                  ^
    

    Instead, you will need to convert your iterators to a sequence explicitly before using them in matcher expressions:

    scala> it.toStream must contain (2)
    

    We recommend you convert (Scala or Java) iterators to Streams, as shown in the previous example, so that you can continue to reap any potential benefits provided by the laziness of the underlying iterator.

    Inspector shorthands

    You can use the Inspectors syntax with matchers as well as assertions. If you have a multi-dimensional collection, such as a list of lists, using Inspectors is your best option:

    val yss =
      List(
        List(1, 2, 3),
        List(1, 2, 3),
        List(1, 2, 3)
      )
    
    forAll (yss) { ys =>
      forAll (ys) { y => y must be > 0 }
    }
    

    For assertions on one-dimensional collections, however, matchers provides "inspector shorthands." Instead of writing:

    val xs = List(1, 2, 3)
    forAll (xs) { x => x must be < 10 }
    

    You can write:

    all (xs) must be < 10
    

    The previous statement asserts that all elements of the xs list must be less than 10. All of the inspectors have shorthands in matchers. Here is the full list:

    • all - succeeds if the assertion holds true for every element
    • atLeast - succeeds if the assertion holds true for at least the specified number of elements
    • atMost - succeeds if the assertion holds true for at most the specified number of elements
    • between - succeeds if the assertion holds true for between the specified minimum and maximum number of elements, inclusive
    • every - same as all, but lists all failing elements if it fails (whereas all just reports the first failing element)
    • exactly - succeeds if the assertion holds true for exactly the specified number of elements

    Here are some examples:

    scala> import org.scalatest.MustMatchers._
    import org.scalatest.MustMatchers._
    
    scala> val xs = List(1, 2, 3, 4, 5)
    xs: List[Int] = List(1, 2, 3, 4, 5)
    
    scala> all (xs) must be > 0
    
    scala> atMost (2, xs) must be >= 4
    
    scala> atLeast (3, xs) must be < 5
    
    scala> between (2, 3, xs) must (be > 1 and be < 5)
    
    scala> exactly (2, xs) must be <= 2
    
    scala> every (xs) must be < 10
    
    scala> // And one that fails...
    
    scala> exactly (2, xs) mustEqual 2
    org.scalatest.exceptions.TestFailedException: 'exactly(2)' inspection failed, because only 1 element
        satisfied the assertion block at index 1:
      at index 0, 1 did not equal 2,
      at index 2, 3 did not equal 2,
      at index 3, 4 did not equal 2,
      at index 4, 5 did not equal 2
    in List(1, 2, 3, 4, 5)
            at ...
    

    Like Inspectors, objects used with inspector shorthands can be any type T for which a Collecting[T, E] is availabe, which by default includes GenTraversable, Java Collection, Java Map, Arrays, and Strings. Here are some examples:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import MustMatchers._
    import MustMatchers._
    
    scala> all (Array(1, 2, 3)) must be < 5
    
    scala> import collection.JavaConverters._
    import collection.JavaConverters._
    
    scala> val js = List(1, 2, 3).asJava
    js: java.util.List[Int] = [1, 2, 3]
    
    scala> all (js) must be < 5
    
    scala> val jmap = Map("a" -> 1, "b" -> 2).asJava
    jmap: java.util.Map[String,Int] = {a=1, b=2}
    
    scala> atLeast(1, jmap) mustBe Entry("b", 2)
    
    scala> atLeast(2, "hello, world!") mustBe 'o'
    

    Single-element collections

    To assert both that a collection contains just one "lone" element as well as something else about that element, you can use the loneElement syntax provided by trait LoneElement. For example, if a Set[Int] must contain just one element, an Int less than or equal to 10, you could write:

    import LoneElement._
    set.loneElement must be <= 10
    

    You can invoke loneElement on any type T for which an implicit Collecting[E, T] is available, where E is the element type returned by the loneElement invocation. By default, you can use loneElement on GenTraversable, Java Collection, Java Map, Array, and String.

    Java collections and maps

    You can use similar syntax on Java collections (java.util.Collection) and maps (java.util.Map). For example, you can check whether a Java Collection or Map is empty, like this:

    javaCollection must be ('empty)
    javaMap must be ('empty)
    

    Even though Java's List type doesn't actually have a length or getLength method, you can nevertheless check the length of a Java List (java.util.List) like this:

    javaList must have length 9
    

    You can check the size of any Java Collection or Map, like this:

    javaMap must have size 20
    javaSet must have size 90
    

    In addition, you can check whether a Java Collection contains a particular element, like this:

    javaCollection must contain ("five")
    

    One difference to note between the syntax supported on Java and Scala collections is that in Java, Map is not a subtype of Collection, and does not actually define an element type. You can ask a Java Map for an "entry set" via the entrySet method, which will return the Map's key/value pairs wrapped in a set of java.util.Map.Entry, but a Map is not actually a collection of Entry. To make Java Maps easier to work with, however, ScalaTest matchers allows you to treat a Java Map as a collection of Entry, and defines a convenience implementation of java.util.Map.Entry in org.scalatest.Entry. Here's how you use it:

    javaMap must contain (Entry(2, 3))
    javaMap must contain oneOf (Entry(2, 3), Entry(3, 4))
    

    You can you alse just check whether a Java Map contains a particular key, or value, like this:

    javaMap must contain key 1
    javaMap must contain value "Howdy"
    

    Strings and Arrays as collections

    You can also use all the syntax described above for Scala and Java collections on Arrays and Strings. Here are some examples:

    scala> import org.scalatest._
    import org.scalatest._
    
    scala> import MustMatchers._
    import MustMatchers._
    
    scala> atLeast (2, Array(1, 2, 3)) must be > 1
    
    scala> atMost (2, "halloo") mustBe 'o'
    
    scala> Array(1, 2, 3) mustBe sorted
    
    scala> "abcdefg" mustBe sorted
    
    scala> Array(1, 2, 3) must contain atMostOneOf (3, 4, 5)
    
    scala> "abc" must contain atMostOneOf ('c', 'd', 'e')
    

    be as an equality comparison

    All uses of be other than those shown previously perform an equality comparison. They work the same as equal when it is used with default equality. This redundancy between be and equals exists in part because it enables syntax that sometimes sounds more natural. For example, instead of writing:

    result must equal (null)
    

    You can write:

    result must be (null)
    

    (Hopefully you won't write that too much given null is error prone, and Option is usually a better, well, option.) As mentioned previously, the other difference between equal and be is that equal delegates the equality check to an Equality typeclass, whereas be always uses default equality. Here are some other examples of be used for equality comparison:

    sum must be (7.0)
    boring must be (false)
    fun must be (true)
    list must be (Nil)
    option must be (None)
    option must be (Some(1))
    

    As with equal used with default equality, using be on arrays results in deep being called on both arrays prior to calling equal. As a result, the following expression would not throw a TestFailedException:

    Array(1, 2) must be (Array(1, 2)) // succeeds (i.e., does not throw TestFailedException)
    

    Because be is used in several ways in ScalaTest matcher syntax, just as it is used in many ways in English, one potential point of confusion in the event of a failure is determining whether be was being used as an equality comparison or in some other way, such as a property assertion. To make it more obvious when be is being used for equality, the failure messages generated for those equality checks will include the word equal in them. For example, if this expression fails with a TestFailedException:

    option must be (Some(1))
    

    The detail message in that TestFailedException will include the words "equal to" to signify be was in this case being used for equality comparison:

    Some(2) was not equal to Some(1)
    

    Being negative

    If you wish to check the opposite of some condition, you can simply insert not in the expression. Here are a few examples:

    result must not be (null)
    sum must not be <= (10)
    mylist must not equal (yourList)
    string must not startWith ("Hello")
    

    Checking that a snippet of code does not compile

    Often when creating libraries you may wish to ensure that certain arrangements of code that represent potential “user errors” do not compile, so that your library is more error resistant. ScalaTest Matchers trait includes the following syntax for that purpose:

    "val a: String = 1" mustNot compile
    

    If you want to ensure that a snippet of code does not compile because of a type error (as opposed to a syntax error), use:

    "val a: String = 1" mustNot typeCheck
    

    Note that the mustNot typeCheck syntax will only succeed if the given snippet of code does not compile because of a type error. A syntax error will still result on a thrown TestFailedException.

    If you want to state that a snippet of code does compile, you can make that more obvious with:

    "val a: Int = 1" must compile
    

    Although the previous three constructs are implemented with macros that determine at compile time whether the snippet of code represented by the string does or does not compile, errors are reported as test failures at runtime.

    Logical expressions with and and or

    You can also combine matcher expressions with and and/or or, however, you must place parentheses or curly braces around the and or or expression. For example, this and-expression would not compile, because the parentheses are missing:

    map must contain key ("two") and not contain value (7) // ERROR, parentheses missing!
    

    Instead, you need to write:

    map must (contain key ("two") and not contain value (7))
    

    Here are some more examples:

    number must (be > (0) and be <= (10))
    option must (equal (Some(List(1, 2, 3))) or be (None))
    string must (
      equal ("fee") or
      equal ("fie") or
      equal ("foe") or
      equal ("fum")
    )
    

    Two differences exist between expressions composed of these and and or operators and the expressions you can write on regular Booleans using its && and || operators. First, expressions with and and or do not short-circuit. The following contrived expression, for example, would print "hello, world!":

    "yellow" must (equal ("blue") and equal { println("hello, world!"); "green" })
    

    In other words, the entire and or or expression is always evaluated, so you'll see any side effects of the right-hand side even if evaluating only the left-hand side is enough to determine the ultimate result of the larger expression. Failure messages produced by these expressions will "short-circuit," however, mentioning only the left-hand side if that's enough to determine the result of the entire expression. This "short-circuiting" behavior of failure messages is intended to make it easier and quicker for you to ascertain which part of the expression caused the failure. The failure message for the previous expression, for example, would be:

    "yellow" did not equal "blue"
    

    Most likely this lack of short-circuiting would rarely be noticeable, because evaluating the right hand side will usually not involve a side effect. One situation where it might show up, however, is if you attempt to and a null check on a variable with an expression that uses the variable, like this:

    map must (not be (null) and contain key ("ouch"))
    

    If map is null, the test will indeed fail, but with a NullArgumentException, not a TestFailedException. Here, the NullArgumentException is the visible right-hand side effect. To get a TestFailedException, you would need to check each assertion separately:

    map must not be (null)
    map must contain key ("ouch")
    

    If map is null in this case, the null check in the first expression will fail with a TestFailedException, and the second expression will never be executed.

    The other difference with Boolean operators is that although && has a higher precedence than ||, and and or have the same precedence. Thus although the Boolean expression (a || b && c) will evaluate the && expression before the || expression, like (a || (b && c)), the following expression:

    traversable must (contain (7) or contain (8) and have size (9))
    

    Will evaluate left to right, as:

    traversable must ((contain (7) or contain (8)) and have size (9))
    

    If you really want the and part to be evaluated first, you'll need to put in parentheses, like this:

    traversable must (contain (7) or (contain (8) and have size (9)))
    

    Working with Options

    You can work with options using ScalaTest's equality, empty, defined, and contain syntax. For example, if you wish to check whether an option is None, you can write any of:

    option mustEqual None
    option mustBe None
    option must === (None)
    option mustBe empty
    

    If you wish to check an option is defined, and holds a specific value, you can write any of:

    option mustEqual Some("hi")
    option mustBe Some("hi")
    option must === (Some("hi"))
    

    If you only wish to check that an option is defined, but don't care what it's value is, you can write:

    option mustBe defined
    

    If you mix in (or import the members of) OptionValues, you can write one statement that indicates you believe an option must be defined and then say something else about its value. Here's an example:

    import org.scalatest.OptionValues._
    option.value must be < 7
    

    As mentioned previously, you can use also use ScalaTest's contain, contain oneOf, and contain noneOf syntax with options:

    Some(2) must contain (2)
    Some(7) must contain oneOf (5, 7, 9)
    Some(0) must contain noneOf (7, 8, 9)
    

    Checking arbitrary properties with have

    Using have, you can check properties of any type, where a property is an attribute of any object that can be retrieved either by a public field, method, or JavaBean-style get or is method, like this:

    book must have (
      'title ("Programming in Scala"),
      'author (List("Odersky", "Spoon", "Venners")),
      'pubYear (2008)
    )
    

    This expression will use reflection to ensure the title, author, and pubYear properties of object book are equal to the specified values. For example, it will ensure that book has either a public Java field or method named title, or a public method named getTitle, that when invoked (or accessed in the field case) results in a the string "Programming in Scala". If all specified properties exist and have their expected values, respectively, execution will continue. If one or more of the properties either does not exist, or exists but results in an unexpected value, a TestFailedException will be thrown that explains the problem. (For the details on how a field or method is selected during this process, see the documentation for HavePropertyMatcherGenerator.)

    When you use this syntax, you must place one or more property values in parentheses after have, seperated by commas, where a property value is a symbol indicating the name of the property followed by the expected value in parentheses. The only exceptions to this rule is the syntax for checking size and length shown previously, which does not require parentheses. If you forget and put parentheses in, however, everything will still work as you'd expect. Thus instead of writing:

    array must have length (3)
    set must have size (90)
    

    You can alternatively, write:

    array must have (length (3))
    set must have (size (90))
    

    If a property has a value different from the specified expected value, a TestFailedError will be thrown with a detailed message that explains the problem. For example, if you assert the following on a book whose title is Moby Dick:

    book must have ('title ("A Tale of Two Cities"))
    

    You'll get a TestFailedException with this detail message:

    The title property had value "Moby Dick", instead of its expected value "A Tale of Two Cities",
    on object Book("Moby Dick", "Melville", 1851)
    

    If you prefer to check properties in a type-safe manner, you can use a HavePropertyMatcher. This would allow you to write expressions such as:

    book must have (
      title ("Programming in Scala"),
      author (List("Odersky", "Spoon", "Venners")),
      pubYear (2008)
    )
    

    These expressions would fail to compile if must is used on an inappropriate type, as determined by the type parameter of the HavePropertyMatcher being used. (For example, title in this example might be of type HavePropertyMatcher[org.publiclibrary.Book]. If used with an appropriate type, such an expression will compile and at run time the property method or field will be accessed directly; i.e., no reflection will be used. See the documentation for HavePropertyMatcher for more information.

    Using length and size with HavePropertyMatchers

    If you want to use length or size syntax with your own custom HavePropertyMatchers, you can do so, but you must write (of [“the type”]) afterwords. For example, you could write:

    book must have (
      title ("A Tale of Two Cities"),
      length (220) (of [Book]),
      author ("Dickens")
    )
    

    Prior to ScalaTest 2.0, “length (22)” yielded a HavePropertyMatcher[Any, Int] that used reflection to dynamically look for a length field or getLength method. In ScalaTest 2.0, “length (22)” yields a MatcherFactory1[Any, Length], so it is no longer a HavePropertyMatcher. The (of [<type>]) syntax converts the the MatcherFactory1[Any, Length] to a HavePropertyMatcher[<type>, Int].

    Checking that an expression matches a pattern

    ScalaTest's Inside trait allows you to make assertions after a pattern match. Here's an example:

    case class Name(first: String, middle: String, last: String)
    
    val name = Name("Jane", "Q", "Programmer")
    
    inside(name) { case Name(first, _, _) =>
      first must startWith ("S")
    }
    

    You can use inside to just ensure a pattern is matched, without making any further assertions, but a better alternative for that kind of assertion is matchPattern. The matchPattern syntax allows you to express that you expect a value to match a particular pattern, no more and no less:

    name must matchPattern { case Name("Sarah", _, _) => }
    

    Using custom matchers

    If none of the built-in matcher syntax (or options shown so far for extending the syntax) satisfy a particular need you have, you can create custom Matchers that allow you to place your own syntax directly after must. For example, class java.io.File has a method isHidden, which indicates whether a file of a certain path and name is hidden. Because the isHidden method takes no parameters and returns Boolean, you can call it using be with a symbol or BePropertyMatcher, yielding assertions like:

    file must be ('hidden)  // using a symbol
    file must be (hidden)   // using a BePropertyMatcher
    

    If it doesn't make sense to have your custom syntax follow be, you might want to create a custom Matcher instead, so your syntax can follow must directly. For example, you might want to be able to check whether a java.io.File's name ends with a particular extension, like this:

    // using a plain-old Matcher
    file must endWithExtension ("txt")
    

    ScalaTest provides several mechanism to make it easy to create custom matchers, including ways to compose new matchers out of existing ones complete with new error messages. For more information about how to create custom Matchers, please see the documentation for the Matcher trait.

    Checking for expected exceptions

    Sometimes you need to test whether a method throws an expected exception under certain circumstances, such as when invalid arguments are passed to the method. With Matchers mixed in, you can check for an expected exception like this:

    an [IndexOutOfBoundsException] must be thrownBy s.charAt(-1)
    

    If charAt throws an instance of StringIndexOutOfBoundsException, this expression will result in that exception. But if charAt completes normally, or throws a different exception, this expression will complete abruptly with a TestFailedException.

    If you need to further isnpect an expected exception, you can capture it using this syntax:

    val thrown = the [IndexOutOfBoundsException] thrownBy s.charAt(-1)
    

    This expression returns the caught exception so that you can inspect it further if you wish, for example, to ensure that data contained inside the exception has the expected values. Here's an example:

    thrown.getMessage must equal ("String index out of range: -1")
    

    If you prefer you can also capture and inspect an expected exception in one statement, like this:

    the [ArithmeticException] thrownBy 1 / 0 must have message "/ by zero"
    the [IndexOutOfBoundsException] thrownBy {
      s.charAt(-1)
    } must have message "String index out of range: -1"
    

    You can also state that no exception must be thrown by some code, like this:

    noException must be thrownBy 0 / 1
    

    Those pesky parens

    Perhaps the most tricky part of writing assertions using ScalaTest matchers is remembering when you need or don't need parentheses, but bearing in mind a few simple rules should help. It is also reassuring to know that if you ever leave off a set of parentheses when they are required, your code will not compile. Thus the compiler will help you remember when you need the parens. That said, the rules are:

    1. Although you don't always need them, you may choose to always put parentheses around right-hand values, such as the 7 in num must equal (7):

    result must equal (4)
    array must have length (3)
    book must have (
      'title ("Programming in Scala"),
      'author (List("Odersky", "Spoon", "Venners")),
      'pubYear (2008)
    )
    option must be ('defined)
    catMap must (contain key (9) and contain value ("lives"))
    keyEvent must be an ('actionKey)
    javaSet must have size (90)
    

    2. Except for length, size and message, you must always put parentheses around the list of one or more property values following a have:

    file must (exist and have ('name ("temp.txt")))
    book must have (
      title ("Programming in Scala"),
      author (List("Odersky", "Spoon", "Venners")),
      pubYear (2008)
    )
    javaList must have length (9) // parens optional for length and size
    

    3. You must always put parentheses around and and or expressions, as in:

    catMap must (contain key (9) and contain value ("lives"))
    number must (equal (2) or equal (4) or equal (8))
    

    4. Although you don't always need them, you may choose to always put parentheses around custom Matchers when they appear directly after not:

    file must exist
    file must not (exist)
    file must (exist and have ('name ("temp.txt")))
    file must (not (exist) and have ('name ("temp.txt"))
    file must (have ('name ("temp.txt") or exist)
    file must (have ('name ("temp.txt") or not (exist))
    

    That's it. With a bit of practice it should become natural to you, and the compiler will always be there to tell you if you forget a set of needed parentheses.

    Note: ScalaTest's matchers are in part inspired by the matchers of RSpec, Hamcrest, and specs2, and its “mustNot compile” syntax by the illTyped macro of shapeless.

  69. trait NonImplicitAssertions extends Assertions

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    Trait that can be mixed into a Suite to disable the lone implicit conversion provided by default in trait Assertions, which trait Suite extends.

    Trait that can be mixed into a Suite to disable the lone implicit conversion provided by default in trait Assertions, which trait Suite extends.

    Currently there is just one implicit conversion provided by default in Suite, the one that adds a === method to anything. If more default implicits are added to Suite in future versions of ScalaTest, they will be added here as well so that this trait will disable all of them.

    This trait can be used to quickly solve a problem in which ScalaTest's default implicit conversion is clashing with those of some other library you need to use in your tests. After mixing in this trait, like this:

    class MySuite extends FunSuite with NonImplicitAssertions {
      // ...
    }
    

    You can write tests using assert (without triple equals), expect, and intercept:

      assert(a < 7)
    
      expect(2) { 1 + 1 }
    
      intercept[IndexOutOfBoundsException] {
        "hi".charAt(-1)
      }
    

  70. trait Notifier extends AnyRef

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    Trait providing an apply method to which status updates about a running suite of tests can be reported.

    Trait providing an apply method to which status updates about a running suite of tests can be reported.

    An Notifier is essentially used to wrap a Reporter and provide easy ways to send status updates to that Reporter via an NoteProvided event. Notifier contains an apply method that takes a string and an optional payload object of type Any. The Notifier will forward the passed alert message string to the Reporter as the message parameter, and the optional payload object as the payload parameter, of an NoteProvided event.

    For insight into the differences between Notifier, Alerter, and Informer, see the main documentation for trait Notifying.

  71. trait Notifying extends AnyRef

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    Trait that contains the note method, which can be used to send a status notification to the reporter.

    Trait that contains the note method, which can be used to send a status notification to the reporter.

    The difference between note and the info method of Informer is that info messages provided during a test are recorded and sent as part of test completion event, whereas note messages are sent right away as NoteProvided messages. For long-running tests, note allows you to send "status notifications" to the reporter right away, so users can track the progress of the long-running tests. By contrast, info messages will only be seen by the user after the test has completed, and are more geared towards specification (such as Given/When/Then messages) than notification.

    The difference between note and the alert method of Alerting is that alert is intended to be used for warnings or notifications of potential problems, whereas note is just for status notifications. In string reporters for which ANSI color is enabled, note notifications are shown in green and alert notifications in yellow.

  72. trait OneInstancePerTest extends SuiteMixin

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    Trait that facilitates a style of testing in which each test is run in its own instance of the suite class to isolate each test from the side effects of the other tests in the suite.

    Trait that facilitates a style of testing in which each test is run in its own instance of the suite class to isolate each test from the side effects of the other tests in the suite.

    Recommended Usage: Trait OneInstancePerTest is intended primarily to serve as a supertrait for ParallelTestExecution and the path traits, to facilitate porting JUnit tests to ScalaTest, and to make it easy for users who prefer JUnit's approach to isolation to obtain similar behavior in ScalaTest.

    If you mix this trait into a Suite, you can initialize shared reassignable fixture variables as well as shared mutable fixture objects in the constructor of the class. Because each test will run in its own instance of the class, each test will get a fresh copy of the instance variables. This is the approach to test isolation taken, for example, by the JUnit framework. OneInstancePerTest can, therefore, be handy when porting JUnit tests to ScalaTest.

    Here's an example of OneInstancePerTest being used in a FunSuite:

    import org.scalatest.FunSuite
    import org.scalatest.OneInstancePerTest
    import collection.mutable.ListBuffer
    
    class MySuite extends FunSuite with OneInstancePerTest {
    
      val builder = new StringBuilder("ScalaTest is ")
      val buffer = new ListBuffer[String]
    
      test("easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    

    OneInstancePerTest is supertrait to ParallelTestExecution, in which running each test in its own instance is intended to make it easier to write suites of tests that run in parallel (by reducing the likelihood of concurrency bugs in those suites.) OneInstancePerTest is also supertrait to the path traits, path.FunSpec and path.FreeSpec, to make it obvious these traits run each test in a new, isolated instance.

    For the details on how OneInstancePerTest works, see the documentation for methods runTests and runTest, which this trait overrides.

  73. trait OptionValues extends AnyRef

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    Trait that provides an implicit conversion that adds a value method to Option, which will return the value of the option if it is defined, or throw TestFailedException if not.

    Trait that provides an implicit conversion that adds a value method to Option, which will return the value of the option if it is defined, or throw TestFailedException if not.

    This construct allows you to express in one statement that an option should be defined and that its value should meet some expectation. Here's an example:

    opt.value should be > 9
    

    Or, using an assertion instead of a matcher expression:

    assert(opt.value > 9)
    

    Were you to simply invoke get on the Option, if the option wasn't defined, it would throw a NoSuchElementException:

    val opt: Option[Int] = None
    
    opt.get should be > 9 // opt.get throws NoSuchElementException
    

    The NoSuchElementException would cause the test to fail, but without providing a stack depth pointing to the failing line of test code. This stack depth, provided by TestFailedException (and a few other ScalaTest exceptions), makes it quicker for users to navigate to the cause of the failure. Without OptionValues, to get a stack depth exception you would need to make two statements, like this:

    val opt: Option[Int] = None
    
    opt should be ('defined) // throws TestFailedException
    opt.get should be > 9
    

    The OptionValues trait allows you to state that more concisely:

    val opt: Option[Int] = None
    
    opt.value should be > 9 // opt.value throws TestFailedException
    

  74. sealed abstract class Outcome extends AnyRef

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    Superclass for the possible outcomes of running a test.

    Superclass for the possible outcomes of running a test.

    Outcome is the result type of the withFixture methods of traits Suite and fixture.Suite, as well as their NoArgTest and OneArgTest function types. The four possible outcomes are:

    • Succeeded - indicates a test succeeded
    • Failed - indicates a test failed and contains an exception describing the failure
    • Canceled - indicates a test was canceled and contains an exception describing the cancelation
    • Pending - indicates a test was pending

    Note that "ignored" does not appear as a type of Outcome, because tests are marked as ignored on the outside and skipped over as the suite executes. So an ignored test never runs, and therefore never has an outcome. By contrast, a test is determined to be pending by running the test and observing the actual outcome. If the test body completes abruptly with a TestPendingException, then the outcome was that the test was pending.

  75. trait OutcomeOf extends AnyRef

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    Trait that contains the outcomeOf method, which executes a passed code block and transforms the outcome into an Outcome, using the same mechanism used by ScalaTest to produce an Outcome when executing a test.

    Trait that contains the outcomeOf method, which executes a passed code block and transforms the outcome into an Outcome, using the same mechanism used by ScalaTest to produce an Outcome when executing a test.

    For an example of outcomeOf in action, see the documentation for class TableFor2.

  76. trait ParallelTestExecution extends OneInstancePerTest

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    Trait that causes that the tests of any suite it is mixed into to be run in parallel if a Distributor is passed to runTests.

    Trait that causes that the tests of any suite it is mixed into to be run in parallel if a Distributor is passed to runTests.

    ScalaTest's normal approach for running suites of tests in parallel is to run different suites in parallel, but the tests of any one suite sequentially. This approach should provide sufficient distribution of the work load in most cases, but some suites may encapsulate multiple long-running tests. Such suites may dominate the execution time of the run. If so, mixing in this trait into just those suites will allow their long-running tests to run in parallel with each other, thereby helping to reduce the total time required to run an entire run.

    To make it easier for users to write tests that run in parallel, this trait runs each test in its own instance of the class. Running each test in its own instance enables tests to use the same instance vars and mutable objects referenced from instance variables without needing to synchronize. Although ScalaTest provides functional approaches to factoring out common test code that can help avoid such issues, running each test in its own instance is an insurance policy that makes running tests in parallel easier and less error prone.

    For the details on how ParallelTestExecution works, see the documentation for methods run, runTests, and runTest, which this trait overrides.

    Note: This trait's implementation of runTest is final, to ensure that behavior related to individual tests are executed by the same thread that executes the actual test. This means, for example, that you won't be allowed to write ...with ParallelTestExecution with BeforeAndAfter. Instead, you'd need to put ParallelTestExecution last, as in: with BeforeAndAfter with ParallelTestExecution. For more details, see the documentation for the runTest method.

  77. trait PartialFunctionValues extends AnyRef

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    Trait that provides an implicit conversion that adds a valueAt method to PartialFunction, which will return the value (result) of the function applied to the argument passed to valueAt, or throw TestFailedException if the partial function is not defined at the argument.

    Trait that provides an implicit conversion that adds a valueAt method to PartialFunction, which will return the value (result) of the function applied to the argument passed to valueAt, or throw TestFailedException if the partial function is not defined at the argument.

    This construct allows you to express in one statement that a partial function should be defined for a particular input, and that its result value should meet some expectation. Here's an example:

    pf.valueAt("IV") should equal (4)
    

    Or, using an assertion instead of a matcher expression:

    assert(pf.valueAt("IV") === 4)
    

    Were you to simply invoke apply on the PartialFunction, passing in an input value, if the partial function wasn't defined at that input, it would throw some exception, but likely not one that provides a stack depth:

    // Note: a Map[K, V] is a PartialFunction[K, V]
    val pf: PartialFunction[String, Int] = Map("I" -> 1, "II" -> 2, "III" -> 3, "IV" -> 4)
    
    pf("V") should equal (5) // pf("V") throws NoSuchElementException
    

    The NoSuchElementException thrown in this situation would cause the test to fail, but without providing a stack depth pointing to the failing line of test code. This stack depth, provided by TestFailedException (and a few other ScalaTest exceptions), makes it quicker for users to navigate to the cause of the failure. Without PartialFunctionValues, to get a stack depth exception you would need to make two statements, like this:

    val pf: PartialFunction[String, Int] = Map("I" -> 1, "II" -> 2, "III" -> 3, "IV" -> 4)
    
    pf.isDefinedAt("V") should be (true) // throws TestFailedException
    pf("V") should equal (5)
    

    The PartialFunctionValues trait allows you to state that more concisely:

    val pf: PartialFunction[String, Int] = Map("I" -> 1, "II" -> 2, "III" -> 3, "IV" -> 4)
    
    pf.valueAt("V") should equal (5) // pf.valueAt("V") throws TestFailedException
    

  78. trait Payloads extends AnyRef

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    Trait facilitating the inclusion of a payload in a thrown ScalaTest exception.

    Trait facilitating the inclusion of a payload in a thrown ScalaTest exception.

    This trait includes a withPayload construct that enables a payload object (or modified payload object) to be included as the payload of a thrown exception.

    Many ScalaTest events include an optional "payload" field that can be used to pass information to a custom reporter. This trait facilitates such customization, by making it easy to insert a payload into a thrown exception, such as a TestFailedException. The thrown exception must mix in Payload. ScalaTest looks for trait Payload and fires any payloads it finds in the relevant ScalaTest event stimulated by the exception, such as a TestFailed event stimulated by a TestFailedException. Here's an example in which a GUI snapshot is included as a payload when a test fails:

    withPayload(generateGUISnapshot()) {
      1 + 1 should === (3)
    }
    

  79. sealed trait PendingStatement extends AnyRef

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    Trait mixed into the result type of the pending statement of trait Assertions, which always throws TestPendingException.

    Trait mixed into the result type of the pending statement of trait Assertions, which always throws TestPendingException.

    This type is used primarily to facilitate the is (pending) syntax of traits FlatSpec, WordSpec, and FLatSpec as well the is (pending) or (pending) syntax of sibling traits in the org.scalatest.fixture package. Because the pending method in Assertions always completes abruptly with an exception, its type would be inferred to be Nothing, which is a relatively common type. To make sure syntax like is (pending) only works with method pending, it is helpful to have a specially named "Nothing" type.

  80. trait PrivateMethodTester extends AnyRef

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    Trait that facilitates the testing of private methods.

    Trait that facilitates the testing of private methods.

    To test a private method, mix in trait PrivateMethodTester and create a PrivateMethod object, like this:

    val decorateToStringValue = PrivateMethod[String]('decorateToStringValue)
    

    The type parameter on PrivateMethod, in this case String, is the result type of the private method you wish to invoke. The symbol passed to the PrivateMethod.apply factory method, in this case 'decorateToStringValue, is the name of the private method to invoke. To test the private method, use the invokePrivate operator, like this:

    targetObject invokePrivate decorateToStringValue(1)
    

    Here, targetObject is a variable or singleton object name referring to the object whose private method you want to test. You pass the arguments to the private method in the parentheses after the PrivateMethod object. The result type of an invokePrivate operation will be the type parameter of the PrivateMethod object, thus you need not cast the result to use it. In other words, after creating a PrivateMethod object, the syntax to invoke the private method looks like a regular method invocation, but with the dot (.) replaced by invokePrivate. The private method is invoked dynamically via reflection, so if you have a typo in the method name symbol, specify the wrong result type, or pass invalid parameters, the invokePrivate operation will compile, but throw an exception at runtime.

    One limitation to be aware of is that you can't use PrivateMethodTester to test a private method declared in a trait, because the class the trait gets mixed into will not declare that private method. Only the class generated to hold method implementations for the trait will have that private method. If you want to test a private method declared in a trait, and that method does not use any state of that trait, you can move the private method to a companion object for the trait and test it using PrivateMethodTester that way. If the private trait method you want to test uses the trait's state, your best options are to test it indirectly via a non-private trait method that calls the private method, or make the private method package access and test it directly via regular static method invocations.

    Also, if you want to use PrivateMethodTester to invoke a parameterless private method, you'll need to use empty parens. Instead of:

    targetObject invokePrivate privateParameterlessMethod
    

    You'll need to write:

    targetObject invokePrivate privateParameterlessMethod()
    

  81. class PropSpec extends PropSpecLike

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    A suite of property-based tests.

    A suite of property-based tests.

    Recommended Usage: Class PropSpec is a good fit for teams that want to write tests exclusively in terms of property checks, and is also a good choice for writing the occasional test matrix when a different style trait is chosen as the main unit testing style.

    Here's an example PropSpec:

    package org.scalatest.examples.propspec
    
    import org.scalatest._
    import prop._
    import scala.collection.immutable._
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with Matchers {
    
      val examples =
        Table(
          "set",
          BitSet.empty,
          HashSet.empty[Int],
          TreeSet.empty[Int]
        )
    
      property("an empty Set should have size 0") {
        forAll(examples) { set =>
          set.size should be (0)
        }
      }
    
      property("invoking head on an empty set should produce NoSuchElementException") {
        forAll(examples) { set =>
          evaluating { set.head } should produce [NoSuchElementException]
        }
      }
    }
    

    You can run a PropSpec by invoking execute on it. This method, which prints test results to the standard output, is intended to serve as a convenient way to run tests from within the Scala interpreter. For example, to run SetSpec from within the Scala interpreter, you could write:

    scala> new SetSpec execute
    

    And you would see:

    SetSpec:
    - an empty Set should have size 0
    - invoking head on an empty Set should produce NoSuchElementException
    

    Or, to run just the “an empty Set should have size 0” method, you could pass that test's name, or any unique substring of the name, such as "size 0" or even just "0". Here's an example:

    scala> new SetSpec execute "size 0"
    SetSpec:
    - an empty Set should have size 0
    

    You can also pass to execute a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation for execute (below) and the ScalaTest shell.

    The execute method invokes a run method that takes two parameters. This run method, which actually executes the suite, will usually be invoked by a test runner, such as run, tools.Runner, a build tool, or an IDE.

    property” is a method, defined in PropSpec, which will be invoked by the primary constructor of SetSpec. You specify the name of the test as a string between the parentheses, and the test code itself between curly braces. The test code is a function passed as a by-name parameter to property, which registers it for later execution.

    A PropSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered with the property method while the PropSpec is in its registration phase. Any attempt to register a test after the PropSpec has entered its ready phase, i.e., after run has been invoked on the PropSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using PropSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, PropSpec provides registration methods that start with ignore instead of property. Here's an example:

    package org.scalatest.examples.suite.ignore
    
    import org.scalatest._
    import prop._
    import scala.collection.immutable._
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with Matchers {
    
      val examples =
        Table(
          "set",
          BitSet.empty,
          HashSet.empty[Int],
          TreeSet.empty[Int]
        )
    
      ignore("an empty Set should have size 0") {
        forAll(examples) { set =>
          set.size should be (0)
        }
      }
    
      property("invoking head on an empty set should produce NoSuchElementException") {
        forAll(examples) { set =>
          evaluating { set.head } should produce [NoSuchElementException]
        }
      }
    }
    

    If you run this version of SetSuite with:

    scala> new SetSpec execute
    

    It will run only the second test and report that the first test was ignored:

    SetSuite:
    - an empty Set should have size 0 !!! IGNORED !!!
    - invoking head on an empty Set should produce NoSuchElementException
    

    Informers

    One of the parameters to PropSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by PropSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event. Here's an example that shows both a direct use as well as an indirect use through the methods of GivenWhenThen:

    package org.scalatest.examples.propspec.info
    
    import org.scalatest._
    import prop._
    import collection.mutable
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with GivenWhenThen {
    
      val examples =
        Table(
          "set",
          mutable.BitSet.empty,
          mutable.HashSet.empty[Int],
          mutable.LinkedHashSet.empty[Int]
        )
    
      property("an element can be added to an empty mutable Set") {
    
        forAll(examples) { set =>
    
          info("----------------")
    
          Given("an empty mutable " + set.getClass.getSimpleName)
          assert(set.isEmpty)
    
          When("an element is added")
          set += 99
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains(99))
        }
      }
    }
    
    If you run this PropSpec from the interpreter, you will see the following output:
    scala> new SetSpec execute
    SetSpec:
    - an element can be added to an empty mutable Set
      + ----------------
      + Given an empty mutable BitSet
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + ----------------
      + Given an empty mutable HashSet
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + ----------------
      + Given an empty mutable LinkedHashSet
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
    
    == Documenters ==

    PropSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event.

    Here's an example PropSpec that uses markup:

    package org.scalatest.examples.propspec.markup
    
    import org.scalatest._
    import prop._
    import collection.mutable
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      val examples =
        Table(
          "set",
          mutable.BitSet.empty,
          mutable.HashSet.empty[Int],
          mutable.LinkedHashSet.empty[Int]
        )
    
      property("an element can be added to an empty mutable Set") {
    
        forAll(examples) { set =>
    
          info("----------------")
    
          Given("an empty mutable " + set.getClass.getSimpleName)
          assert(set.isEmpty)
    
          When("an element is added")
          set += 99
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains(99))
        }
    
        markup("This test finished with a **bold** statement!")
      }
    }
    

    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter:

    Notifiers and alerters

    ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:

    package org.scalatest.examples.propspec.note
    
    import org.scalatest._
    import prop._
    import collection.mutable
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks {
    
      val examples =
        Table(
          "set",
          mutable.BitSet.empty,
          mutable.HashSet.empty[Int],
          mutable.LinkedHashSet.empty[Int]
        )
    
      property("an element can be added to an empty mutable Set") {
    
        info("info is recorded")
        markup("markup is *also* recorded")
        note("notes are sent immediately")
        alert("alerts are also sent immediately")
    
        forAll(examples) { set =>
    
          assert(set.isEmpty)
          set += 99
          assert(set.size === 1)
          assert(set.contains(99))
        }
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
      + notes are sent immediately
      + alerts are also sent immediately
    - an element can be added to an empty mutable Set
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests ==

    A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later.

    To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException.

    Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (The code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented.

    You can mark tests pending in PropSpec like this:

    import org.scalatest._
    import prop._
    import scala.collection.immutable._
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with Matchers {
    
      val examples =
        Table(
          "set",
          BitSet.empty,
          HashSet.empty[Int],
          TreeSet.empty[Int]
        )
    
      property("an empty Set should have size 0") (pending)
    
      property("invoking head on an empty set should produce NoSuchElementException") {
        forAll(examples) { set =>
          evaluating { set.head } should produce [NoSuchElementException]
        }
      }
    }
    

    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of SetSuite with:

    scala> new SetSuite execute
    

    It will run both tests, but report that first test is pending. You'll see:

    SetSuite:
    - An empty Set should have size 0 (pending)
    - Invoking head on an empty Set should produce NoSuchElementException
    

    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code.

    One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait.

    Tagging tests

    A PropSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a PropSpec, groups of tests can optionally be included and/or excluded. To tag a PropSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for PropSpecs like this:

    package org.scalatest.examples.propspec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    

    Given these definitions, you could place PropSpec tests into groups like this:

    import org.scalatest._
    import prop._
    import scala.collection.immutable._
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with Matchers {
    
      val examples =
        Table(
          "set",
          BitSet.empty,
          HashSet.empty[Int],
          TreeSet.empty[Int]
        )
    
      property("an empty Set should have size 0", SlowTest) {
        forAll(examples) { set =>
          set.size should be (0)
        }
      }
    
      property("invoking head on an empty set should produce NoSuchElementException",
          SlowTest, DbTest) {
    
        forAll(examples) { set =>
          evaluating { set.head } should produce [NoSuchElementException]
        }
      }
    }
    

    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag.

    The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run.

    Shared fixtures

    A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code.

    ScalaTest recommends three techniques to eliminate such code duplication:

    • Refactor using Scala
    • Override withFixture
    • Mix in a before-and-after trait

    Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution.

    The techniques in PropSpec are identical to those in FunSuite, but with “test” replaced by “property”. The following table summarizes the options with a link to the relevant documentation for trait FunSuite:

    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.

    Using PropSpec to implement a test matrix

    Using fixture-context objects in a PropSpec is a good way to implement a test matrix. What is the matrix? A test matrix is a series of tests that you need to run on a series of subjects. For example, The Scala API contains many implementations of trait Set. Every implementation must obey the contract of Set. One property of any Set is that an empty Set should have size 0, another is that invoking head on an empty Set should give you a NoSuchElementException, and so on. Already you have a matrix, where rows are the properties and the columns are the set implementations:

     BitSetHashSetTreeSet
    An empty Set should have size 0passpasspass
    Invoking head on an empty set should produce NoSuchElementExceptionpasspasspass

    One way to implement this test matrix is to define a trait to represent the columns (in this case, BitSet, HashSet, and TreeSet) as elements in a single-dimensional Table. Each element in the Table represents one Set implementation. Because different properties may require different fixture instances for those implementations, you can define a trait to hold the examples, like this:

    trait SetExamples extends Tables {
    
      def examples = Table("set", bitSet, hashSet, treeSet)
    
      def bitSet: BitSet
      def hashSet: HashSet[Int]
      def treeSet: TreeSet[Int]
    }
    

    Given this trait, you could provide empty sets in one implementation of SetExamples, and non-empty sets in another. Here's how you might provide empty set examples:

    class EmptySetExamples extends SetExamples {
      def bitSet = BitSet.empty
      def hashSet = HashSet.empty[Int]
      def treeSet = TreeSet.empty[Int]
    }
    

    And here's how you might provide set examples with one item each:

    class SetWithOneItemExamples extends SetExamples {
      def bitSet = BitSet(1)
      def hashSet = HashSet(1)
      def treeSet = TreeSet(1)
    }
    

    Armed with these example classes, you can define checks of properties that require empty or non-empty set fixtures by using instances of these classes as fixture-context objects. In other words, the columns of the test matrix are implemented as elements of a one-dimensional table of fixtures, the rows are implemented as property clauses of a PropSpec.

    Here's a complete example that checks the two properties mentioned previously:

    package org.scalatest.examples.propspec.matrix
    
    import org.scalatest._
    import org.scalatest.prop._
    import scala.collection.immutable._
    
    trait SetExamples extends Tables {
    
      def examples = Table("set", bitSet, hashSet, treeSet)
    
      def bitSet: BitSet
      def hashSet: HashSet[Int]
      def treeSet: TreeSet[Int]
    }
    
    class EmptySetExamples extends SetExamples {
      def bitSet = BitSet.empty
      def hashSet = HashSet.empty[Int]
      def treeSet = TreeSet.empty[Int]
    }
    
    class SetSpec extends PropSpec with TableDrivenPropertyChecks with Matchers {
    
      property("an empty Set should have size 0") {
        new EmptySetExamples {
          forAll(examples) { set =>
            set.size should be (0)
          }
        }
      }
    
      property("invoking head on an empty set should produce NoSuchElementException") {
        new EmptySetExamples {
          forAll(examples) { set =>
            evaluating { set.head } should produce [NoSuchElementException]
          }
        }
      }
    }
    

    One benefit of this approach is that the compiler will help you when you need to add either a new row or column to the matrix. In either case, you'll need to ensure all cells are checked to get your code to compile.

    Shared tests

    Sometimes you may want to run the same test code on different fixture objects. That is to say, you may want to write tests that are "shared" by different fixture objects. You accomplish this in a PropSpec in the same way you would do it in a FunSuite, except instead of test you say property, and instead of testsFor you say propertiesFor. For more information, see the Shared tests section of FunSuite's documentation.

  82. trait PropSpecLike extends Suite with TestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class PropSpec, which represents a suite of property-based tests.

    Implementation trait for class PropSpec, which represents a suite of property-based tests.

    PropSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of PropSpec into some other class, you can use this trait instead, because class PropSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of PropSpec.

  83. trait RandomTestOrder extends OneInstancePerTest

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    Trait that causes tests to be run in pseudo-random order.

    Trait that causes tests to be run in pseudo-random order.

    Although the tests are run in pseudo-random order, events will be fired in the “normal” order for the Suite that mixes in this trait, as determined by runTests.

    The purpose of this trait is to reduce the likelihood of unintentional order dependencies between tests in the same test class.

  84. trait Reporter extends AnyRef

    Permalink

    Trait whose instances collect the results of a running suite of tests and presents those results in some way to the user.

    Trait whose instances collect the results of a running suite of tests and presents those results in some way to the user. Instances of this trait can be called "report functions" or "reporters."

    Reporters receive test results via fifteen events. Each event is fired to pass a particular kind of information to the reporter. The events are:

    Reporters may be implemented such that they only present some of the reported events to the user. For example, you could define a reporter class that does nothing in response to SuiteStarting events. Such a class would always ignore SuiteStarting events.

    The term test as used in the TestStarting, TestSucceeded, and TestFailed event names is defined abstractly to enable a wide range of test implementations. ScalaTest's style traits (subclasse of trait Suite) fire TestStarting to indicate they are about to invoke one of their tests, TestSucceeded to indicate a test returned normally, and TestFailed to indicate a test completed abruptly with an exception. Although the execution of a Suite subclass's tests will likely be a common event reported via the TestStarting, TestSucceeded, and TestFailed events, because of the abstract definition of “test” used by the the event classes, these events are not limited to this use. Information about any conceptual test may be reported via the TestStarting, TestSucceeded, and TestFailed events.

    Likewise, the term suite as used in the SuiteStarting, SuiteAborted, and SuiteCompleted event names is defined abstractly to enable a wide range of suite implementations. Object Runner fires SuiteStarting to indicate it is about to invoke run on a Suite, SuiteCompleted to indicate a Suite's run method returned normally, and SuiteAborted to indicate a Suite's run method completed abruptly with an exception. Similarly, class Suite fires SuiteStarting to indicate it is about to invoke run on a nested Suite, SuiteCompleted to indicate a nested Suite's run method returned normally, and SuiteAborted to indicate a nested Suite's run method completed abruptly with an exception. Although the execution of a Suite's run method will likely be a common event reported via the SuiteStarting, SuiteAborted, and SuiteCompleted events, because of the abstract definition of "suite" used by the event classes, these events are not limited to this use. Information about any conceptual suite may be reported via the SuiteStarting, SuiteAborted, and SuiteCompleted events.

    Extensibility

    You can create classes that extend Reporter to report test results in custom ways, and to report custom information passed as an event "payload." Reporter classes can handle events in any manner, including doing nothing.

  85. trait ResourcefulReporter extends Reporter

    Permalink

    Subtrait of Reporter that contains a dispose method for releasing any finite, non-memory resources, such as file handles, held by the Reporter.

    Subtrait of Reporter that contains a dispose method for releasing any finite, non-memory resources, such as file handles, held by the Reporter. Runner will invoke dispose on any ResourcefulReporter when it no longer needs the Reporter.

  86. trait Retries extends AnyRef

    Permalink

    Provides methods that can be used in withFixture implementations to retry tests in various scenarios.

    Provides methods that can be used in withFixture implementations to retry tests in various scenarios.

    Trait Retries is intended to help you deal with “flickers”—tests that usually pass, but occasionally fail. The best way to deal with such tests is to fix them so they always pass. Sometimes, however, this is not practical. In such cases, flickers can waste your time by forcing you to investigate test failures that turn out to be flickers. Or worse, like the boy who cried wolf, the flickers may train you an your colleagues to not pay attention to failures such that you don't notice real problems, at least not in a timely manner.

    Trait Retries offers methods that will retry a failed and/or canceled test once, on the same thread, with or without a delay. These methods take a block that results in Outcome, and are intended to be used in withFixture methods. You should be very selective about which tests you retry, retrying those for which you have good evidence to conclude they are flickers. Thus it is recommended you only retry tests that are tagged with Retryable, and only tag tests as such once they have flickered consistently for a while, and only after you invested a reasonable effort into fixing them properly.

    Here's an example showing how you might use Retries:

    package org.scalatest.examples.tagobjects.retryable
    
    import org.scalatest._
    import tagobjects.Retryable
    
    class SetSpec extends FlatSpec with Retries {
    
      override def withFixture(test: NoArgTest) = {
        if (isRetryable(test))
          withRetry { super.withFixture(test) }
        else
          super.withFixture(test)
      }
    
      "An empty Set" should "have size 0" taggedAs(Retryable) in {
        assert(Set.empty.size === 0)
      }
    }
    

  87. class SafeFeatureSpec extends SafeFeatureSpecLike

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    A suite of tests in which each test represents one scenario of a feature.

    A suite of tests in which each test represents one scenario of a feature. SafeFeatureSpec is intended for writing tests that are "higher level" than unit tests, for example, integration tests, functional tests, and acceptance tests. You can use SafeFeatureSpec for unit testing if you prefer, however.

    Recommended Usage: Class SafeFeatureSpec is primarily intended for acceptance testing, including facilitating the process of programmers working alongside non-programmers to define the acceptance requirements.

    Although not required, SafeFeatureSpec is often used together with GivenWhenThen to express acceptance requirements in more detail. Here's an example:

    package org.scalatest.examples.featurespec
    
    import org.scalatest._
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends SafeFeatureSpec with GivenWhenThen {
    
      info("As a TV set owner")
      info("I want to be able to turn the TV on and off")
      info("So I can watch TV when I want")
      info("And save energy when I'm not watching TV")
    
      feature("TV power button") {
        scenario("User presses power button when TV is off") {
    
          Given("a TV set that is switched off")
          val tv = new TVSet
          assert(!tv.isOn)
    
          When("the power button is pressed")
          tv.pressPowerButton()
    
          Then("the TV should switch on")
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on") {
    
          Given("a TV set that is switched on")
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
    
          When("the power button is pressed")
          tv.pressPowerButton()
    
          Then("the TV should switch off")
          assert(!tv.isOn)
        }
      }
    }
    

    Note: for more information on the calls to Given, When, and Then, see the documentation for trait GivenWhenThen and the Informers section below.

    A SafeFeatureSpec contains feature clauses and scenarios. You define a feature clause with feature, and a scenario with scenario. Both feature and scenario are methods, defined in SafeFeatureSpec, which will be invoked by the primary constructor of StackSafeFeatureSpec. A feature clause describes a feature of the subject (class or other entity) you are specifying and testing. In the previous example, the subject under specification and test is a Set. The feature being specified and tested is the behavior of a Set when it is empty and head is invoked. With each scenario you provide a string (the spec text) that specifies the behavior of the subject for one scenario in which the feature may be used, and a block of code that tests that behavior. You place the spec text between the parentheses, followed by the test code between curly braces. The test code will be wrapped up as a function passed as a by-name parameter to scenario, which will register the test for later execution.

    A SafeFeatureSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Scenarios can only be registered with the scenario method while the SafeFeatureSpec is in its registration phase. Any attempt to register a scenario after the SafeFeatureSpec has entered its ready phase, i.e., after run has been invoked on the SafeFeatureSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using SafeFeatureSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Each scenario represents one test. The name of the test is the spec text passed to the scenario method. The feature name does not appear as part of the test name. In a SafeFeatureSpec, therefore, you must take care to ensure that each test has a unique name (in other words, that each scenario has unique spec text).

    When you run a SafeFeatureSpec, it will send Formatters in the events it sends to the Reporter. ScalaTest's built-in reporters will report these events in such a way that the output is easy to read as an informal specification of the subject being tested. For example, were you to run TVSetSpec from within the Scala interpreter:

    scala> new TVSetSpec execute
    

    You would see:

    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is off
        Given a TV set that is switched off
        When the power button is pressed
        Then the TV should switch on
      Scenario: User presses power button when TV is on
        Given a TV set that is switched on
        When the power button is pressed
        Then the TV should switch off
    

    Or, to run just the “Feature: TV power button Scenario: User presses power button when TV is on” method, you could pass that test's name, or any unique substring of the name, such as "TV is on". Here's an example:

    scala> new TVSetSpec execute "TV is on"
    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is on
        Given a TV set that is switched on
        When the power button is pressed
        Then the TV should switch off
    

    You can also pass to execute a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation for execute (below) and the ScalaTest shell.

    The execute method invokes a run method that takes two parameters. This run method, which actually executes the suite, will usually be invoked by a test runner, such as run, tools.Runner, a build tool, or an IDE.

    Note: Trait SafeFeatureSpec's syntax is in part inspired by Cucumber, a Ruby BDD framework.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, SafeFeatureSpec provides registration methods that start with ignore instead of scenario. For example, to temporarily disable the test named addition, just change “scenario” into “ignore,” like this:

    package org.scalatest.examples.featurespec.ignore
    
    import org.scalatest.SafeFeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends SafeFeatureSpec {
    
      feature("TV power button") {
        ignore("User presses power button when TV is off") {
          val tv = new TVSet
          assert(!tv.isOn)
          tv.pressPowerButton()
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on") {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new TVSetSpec execute
    
    It will run only the second scenario and report that the first scenario was ignored:
    TVSetSpec:
    Feature: TV power button
      Scenario: User presses power button when TV is off !!! IGNORED !!!
      Scenario: User presses power button when TV is on
    
    == Informers ==

    One of the parameters to SafeFeatureSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the default reporting done by SafeFeatureSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a scenario to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by SafeFeatureSpec to pass such information to the reporter. You can see this in action in the initial example of this trait's documentation.

    Documenters

    SafeFeatureSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example FlatSpec that uses markup:

    package org.scalatest.examples.featurespec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFeatureSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
         def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      feature("An element can be added to an empty mutable Set") {
        scenario("When an element is added to an empty mutable Set") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.featurespec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFeatureSpec {
    
      feature("An element can be added to an empty mutable Set") {
        scenario("When an element is added to an empty mutable Set") {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    Feature: An element can be added to an empty mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
      Scenario: When an element is added to an empty mutable Set
        info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. You can mark tests as pending in a SafeFeatureSpec like this:
    package org.scalatest.examples.featurespec.pending
    
    import org.scalatest.SafeFeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends SafeFeatureSpec {
    
      feature("TV power button") {
    
        scenario("User presses power button when TV is off") (pending)
    
        scenario("User presses power button when TV is on") {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of TVSetSpec with:
    scala> new TVSetSpec execute
    
    It will run both tests, but report that When empty should have size 0 is pending. You'll see:
    TVSetSpec:
    Feature: TV power button
      Scenario: User presses power button when TV is off (pending)
      Scenario: User presses power button when TV is on
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a SafeFeatureSpec:
    package org.scalatest.examples.featurespec.infopending
    
    import org.scalatest._
    
    class TVSet {
      private var on: Boolean = false
    
      def isOn: Boolean = on
    
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends SafeFeatureSpec with GivenWhenThen {
    
      info("As a TV set owner")
      info("I want to be able to turn the TV on and off")
      info("So I can watch TV when I want")
      info("And save energy when I'm not watching TV")
    
      feature("TV power button") {
        scenario("User presses power button when TV is off") {
          Given("a TV that is switched off")
          When("the power button is pressed")
          Then("the TV should switch on")
          pending
        }
    
        scenario("User presses power button when TV is on") {
          Given("a TV that is switched on")
          When("the power button is pressed")
          Then("the TV should switch off")
          pending
        }
      }
    }
    
    Would yield the following output when run in the interpreter:
    scala> new TVSetSpec execute
    TVSetSpec:
    As a TV set owner
    I want to be able to turn the TV on and off
    So I can watch TV when I want
    And save energy when I'm not watching TV
    Feature: TV power button
      Scenario: User presses power button when TV is off (pending)
        Given a TV that is switched off
        When the power button is pressed
        Then the TV should switch on
      Scenario: User presses power button when TV is on (pending)
        Given a TV that is switched on
        When the power button is pressed
        Then the TV should switch off 
    
    == Tagging tests == A SafeFeatureSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a SafeFeatureSpec, groups of tests can optionally be included and/or excluded. To tag a SafeFeatureSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for SafeFeatureSpecs like this:
    package org.scalatest.examples.featurespec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place SafeFeatureSpec tests into groups like this:
    import org.scalatest.SafeFeatureSpec
    
    class TVSet {
      private var on: Boolean = false
      def isOn: Boolean = on
      def pressPowerButton() {
        on = !on
      }
    }
    
    class TVSetSpec extends SafeFeatureSpec {
    
      feature("TV power button") {
        scenario("User presses power button when TV is off", SlowTest) {
          val tv = new TVSet
          assert(!tv.isOn)
          tv.pressPowerButton()
          assert(tv.isOn)
        }
    
        scenario("User presses power button when TV is on", SlowTest, DbTest) {
          val tv = new TVSet
          tv.pressPowerButton()
          assert(tv.isOn)
          tv.pressPowerButton()
          assert(!tv.isOn)
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a SafeFeatureSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.featurespec.getfixture
    
    import org.scalatest.SafeFeatureSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFeatureSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is designed to ")
          val buffer = new ListBuffer[String]
        }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          val f = fixture
          f.builder.append("encourage clear code!")
          assert(f.builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        scenario("User needs to understand what the tests are doing") {
          val f = fixture
          f.builder.append("be easy to reason about!")
          assert(f.builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.featurespec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.SafeFeatureSpec
    
    class ExampleSpec extends SafeFeatureSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is designed to ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is", "designed", "to")
      }
    
      feature("Simplicity") {
        // This test needs the StringBuilder fixture
        scenario("User needs to read test code written by others") {
          new Builder {
            builder.append("encourage clear code!")
            assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          }
        }
    
        // This test needs the ListBuffer[String] fixture
        scenario("User needs to understand what the tests are doing") {
          new Buffer {
            buffer += ("be", "easy", "to", "reason", "about!")
            assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy", "to", "reason", "about!"))
          }
        }
    
        // This test needs both the StringBuilder and ListBuffer
        scenario("User needs to write tests") {
          new Builder with Buffer {
            builder.append("be easy to learn!")
            buffer += ("be", "easy", "to", "remember", "how", "to", "write!")
            assert(builder.toString === "ScalaTest is designed to be easy to learn!")
            assert(buffer === List("ScalaTest", "is", "designed", "to", "be", "easy",
              "to", "remember", "how", "to", "write!"))
          }
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. That is to say, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:
    package org.scalatest.examples.featurespec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends SafeFeatureSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      scenario("This scenario should succeed") {
        assert(1 + 1 === 2)
      }
    
      scenario("This scenario should fail") {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSpec execute
    ExampleSpec:
    Scenario: This scenario should succeed
    Scenario: This scenario should fail *** FAILED ***
      2 did not equal 3 (:115)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.featurespec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.SafeFeatureSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends SafeFeatureSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is designed to ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is designed to ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      feature("Simplicity") {
        // This test needs the file fixture
        scenario("User needs to read test code written by others") {
          withFile { (file, writer) =>
            writer.write("encourage clear code!")
            writer.flush()
            assert(file.length === 46)
          }
        }
        // This test needs the database fixture
        scenario("User needs to understand what the tests are doing") {
          withDatabase { db =>
            db.append("be easy to reason about!")
            assert(db.toString === "ScalaTest is designed to be easy to reason about!")
          }
        }
        // This test needs both the file and the database
        scenario("User needs to write tests") {
          withDatabase { db =>
            withFile { (file, writer) => // loan-fixture methods compose
              db.append("be easy to learn!")
              writer.write("be easy to remember how to write!")
              writer.flush()
              assert(db.toString === "ScalaTest is designed to be easy to learn!")
              assert(file.length === 58)
            }
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.SafeFeatureSpec and overriding withFixture(OneArgTest). Each test in a fixture.SafeFeatureSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.featurespec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.SafeFeatureSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is designed to be ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") { f =>
          f.writer.write("encourage clear code!")
          f.writer.flush()
          assert(f.file.length === 49)
        }
    
        scenario("User needs to understand what the tests are doing") { f =>
          f.writer.write("be easy to reason about!")
          f.writer.flush()
          assert(f.file.length === 52)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.SafeFeatureSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.featurespec.beforeandafter
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFeatureSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is designed to ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.featurespec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is designed to ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFeatureSpec with Builder with Buffer {
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
          buffer += "easy"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.featurespec.composingbeforeandaftereach
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is designed to ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFeatureSpec with Builder with Buffer {
    
      feature("Simplicity") {
        scenario("User needs to read test code written by others") {
          builder.append("encourage clear code!")
          assert(builder.toString === "ScalaTest is designed to encourage clear code!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
    
        scenario("User needs to understand what the tests are doing") {
          builder.append("be easy to reason about!")
          assert(builder.toString === "ScalaTest is designed to be easy to reason about!")
          assert(buffer.isEmpty)
          buffer += "easy"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared scenarios == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a SafeFeatureSpec, you first place shared tests (i.e., shared scenarios) in behavior functions. These behavior functions will be invoked during the construction phase of any SafeFeatureSpec that uses them, so that the scenarios they contain will be registered as scenarios in that SafeFeatureSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several scenarios that make sense any time the stack is non-empty. Thus you'd ideally want to run those same scenarios for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these scenarios out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your SafeFeatureSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared scenarios are run for all three fixtures. You can define a behavior function that encapsulates these shared scenarios inside the SafeFeatureSpec that uses them. If they are shared between different SafeFeatureSpecs, however, you could also define them in a separate trait that is mixed into each SafeFeatureSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared scenarios for non-full stacks:
    import org.scalatest.SafeFeatureSpec
    import org.scalatest.GivenWhenThen
    import org.scalatestexamples.helpers.Stack
    
    trait SafeFeatureSpecStackBehaviors { this: SafeFeatureSpec with GivenWhenThen =>
    
      def nonEmptyStack(createNonEmptyStack: => Stack[Int], lastItemAdded: Int) {
    
        scenario("empty is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
    
          When("empty is invoked on the stack")
          Then("empty returns false")
          assert(!stack.empty)
        }
    
        scenario("peek is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
          val size = stack.size
    
          When("peek is invoked on the stack")
          Then("peek returns the last item added")
          assert(stack.peek === lastItemAdded)
    
          And("the size of the stack is the same as before")
          assert(stack.size === size)
        }
    
        scenario("pop is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
    
          Given("a non-empty stack")
          val stack = createNonEmptyStack
          val size = stack.size
    
          When("pop is invoked on the stack")
          Then("pop returns the last item added")
          assert(stack.pop === lastItemAdded)
    
          And("the size of the stack one less than before")
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(createNonFullStack: => Stack[Int]) {
    
        scenario("full is invoked on this non-full stack: " + createNonFullStack.toString) {
    
          Given("a non-full stack")
          val stack = createNonFullStack
    
          When("full is invoked on the stack")
          Then("full returns false")
          assert(!stack.full)
        }
    
        scenario("push is invoked on this non-full stack: " + createNonFullStack.toString) {
    
          Given("a non-full stack")
          val stack = createNonFullStack
          val size = stack.size
    
          When("push is invoked on the stack")
          stack.push(7)
    
          Then("the size of the stack is one greater than before")
          assert(stack.size === size + 1)
    
          And("the top of the stack contains the pushed value")
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but SafeFeatureSpec offers a DSL for the purpose, which looks like this:
    scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    scenariosFor(nonFullStack(stackWithOneItem))
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    scenariosFor(nonEmptyStack) // assuming lastValuePushed is also in scope inside nonEmptyStack
    scenariosFor(nonFullStack)
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    import org.scalatest.SafeFeatureSpec
    import org.scalatest.GivenWhenThen
    import org.scalatestexamples.helpers.Stack
    
    class StackSafeFeatureSpec extends SafeFeatureSpec with GivenWhenThen with SafeFeatureSpecStackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      feature("A Stack is pushed and popped") {
    
        scenario("empty is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("empty is invoked on the stack")
          Then("empty returns true")
          assert(stack.empty)
        }
    
        scenario("peek is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("peek is invoked on the stack")
          Then("peek throws IllegalStateException")
          intercept[IllegalStateException] {
            stack.peek
          }
        }
    
        scenario("pop is invoked on an empty stack") {
    
          Given("an empty stack")
          val stack = emptyStack
    
          When("pop is invoked on the stack")
          Then("pop throws IllegalStateException")
          intercept[IllegalStateException] {
            emptyStack.pop
          }
        }
    
        scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
        scenariosFor(nonFullStack(stackWithOneItem))
    
        scenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
        scenariosFor(nonFullStack(stackWithOneItemLessThanCapacity))
    
        scenario("full is invoked on a full stack") {
    
          Given("an full stack")
          val stack = fullStack
    
          When("full is invoked on the stack")
          Then("full returns true")
          assert(stack.full)
        }
    
        scenariosFor(nonEmptyStack(fullStack, lastValuePushed))
    
        scenario("push is invoked on a full stack") {
    
          Given("an full stack")
          val stack = fullStack
    
          When("push is invoked on the stack")
          Then("push throws IllegalStateException")
          intercept[IllegalStateException] {
            stack.push(10)
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> (new StackSafeFeatureSpec).execute()
    Feature: A Stack is pushed and popped
      Scenario: empty is invoked on an empty stack
        Given an empty stack
        When empty is invoked on the stack
        Then empty returns true
      Scenario: peek is invoked on an empty stack
        Given an empty stack
        When peek is invoked on the stack
        Then peek throws IllegalStateException
      Scenario: pop is invoked on an empty stack
        Given an empty stack
        When pop is invoked on the stack
        Then pop throws IllegalStateException
      Scenario: empty is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: full is invoked on this non-full stack: Stack(9)
        Given a non-full stack
        When full is invoked on the stack
        Then full returns false
      Scenario: push is invoked on this non-full stack: Stack(9)
        Given a non-full stack
        When push is invoked on the stack
        Then the size of the stack is one greater than before
        And the top of the stack contains the pushed value
      Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: full is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-full stack
        When full is invoked on the stack
        Then full returns false
      Scenario: push is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
        Given a non-full stack
        When push is invoked on the stack
        Then the size of the stack is one greater than before
        And the top of the stack contains the pushed value
      Scenario: full is invoked on a full stack
        Given an full stack
        When full is invoked on the stack
        Then full returns true
      Scenario: empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When empty is invoked on the stack
        Then empty returns false
      Scenario: peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When peek is invoked on the stack
        Then peek returns the last item added
        And the size of the stack is the same as before
      Scenario: pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
        Given a non-empty stack
        When pop is invoked on the stack
        Then pop returns the last item added
        And the size of the stack one less than before
      Scenario: push is invoked on a full stack
        Given an full stack
        When push is invoked on the stack
        Then push throws IllegalStateException
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. In a SafeFeatureSpec there is no nesting construct analogous to FunSpec's describe clause. Therefore, you need to do a bit of extra work to ensure that the test names are unique. If a duplicate test name problem shows up in a SafeFeatureSpec, you'll need to pass in a prefix or suffix string to add to each test name. You can pass this string the same way you pass any other data needed by the shared tests, or just call toString on the shared fixture object. This is the approach taken by the previous SafeFeatureSpecStackBehaviors example. Given this SafeFeatureSpecStackBehaviors trait, calling it with the stackWithOneItem fixture, like this:
    scenariosFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    
    yields test names: - empty is invoked on this non-empty stack: Stack(9) - peek is invoked on this non-empty stack: Stack(9) - pop is invoked on this non-empty stack: Stack(9) Whereas calling it with the stackWithOneItemLessThanCapacity fixture, like this:
    scenariosFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
    
    yields different test names: - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)

  88. trait SafeFeatureSpecLike extends Suite with SafeTestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class SafeFeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    Implementation trait for class SafeFeatureSpec, which represents a suite of tests in which each test represents one scenario of a feature.

    SafeFeatureSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of SafeFeatureSpec into some other class, you can use this trait instead, because class SafeFeatureSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of SafeFeatureSpec.

  89. class SafeFlatSpec extends SafeFlatSpecLike

    Permalink

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Recommended Usage: Class SafeFlatSpec is a good first step for teams wishing to move from xUnit to BDD, because its structure is flat like xUnit, so simple and familiar, but the test names must be written in a specification style: “X should Y,” “A must B,” etc.

    Trait SafeFlatSpec is so named because your specification text and tests line up flat against the left-side indentation level, with no nesting needed. Here's an example SafeFlatSpec:

    package org.scalatest.examples.flatspec
    
    import org.scalatest.SafeFlatSpec
    
    class SetSpec extends SafeFlatSpec {
    
      behavior of "An empty Set"
    
      it should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    Note: you can use must or can as well as should in a SafeFlatSpec. For example, instead of it should "pop..., you could write it must "pop... or it can "pop....

    Instead of using a behavior of clause, you can alternatively use a shorthand syntax in which you replace the first it with the subject string, like this:

    package org.scalatest.examples.flatspec
    
    import org.scalatest.SafeFlatSpec
    
    class SetSpec extends SafeFlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    Running either of the two previous three versions of SetSpec in the Scala interpreter would yield:

    An empty Set
    - should have size 0
    - should produce NoSuchElementException when head is invoked
    

    In a SafeFlatSpec you write a one (or more) sentence specification for each bit of behavior you wish to specify and test. Each specification sentence has a "subject," which is sometimes called the system under test (or SUT). The subject is the entity being specified and tested and also serves as the subject of the sentences you write for each test. Often you will want to write multiple tests for the same subject. In a SafeFlatSpec, you name the subject once, with a behavior of clause or its shorthand, then write tests for that subject with it should/must/can "do something" phrases. Each it refers to the most recently declared subject. For example, the four tests shown in this snippet are all testing a stack that contains one item:

    behavior of "A Stack (with one item)"
    
    it should "be non-empty" in {}
    
    it should "return the top item on peek" in {}
    
    it should "not remove the top item on peek" in {}
    
    it should "remove the top item on pop" in {}
    

    The same is true if the tests are written using the shorthand notation:

    "A Stack (with one item)" should "be non-empty" in {}
    
    it should "return the top item on peek" in {}
    
    it should "not remove the top item on peek" in {}
    
    it should "remove the top item on pop" in {}
    

    In a SafeFlatSpec, therefore, to figure out what "it" means, you just scan vertically until you find the most recent use of behavior of or the shorthand notation.

    Because sometimes the subject could be plural, you can alternatively use they instead of it:

    "The combinators" should "be easy to learn" in {}
    
    they should "be efficient" in {}
    
    they should "do something cool" in {}
    

    A SafeFlatSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered while the SafeFlatSpec is in its registration phase. Any attempt to register a test after the SafeFlatSpec has entered its ready phase, i.e., after run has been invoked on the SafeFlatSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using SafeFlatSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, SafeFlatSpec provides a method ignore that can be used instead of it or they to register a test. For example, to temporarily disable the test with the name "An empty Set should produce NoSuchElementException when head is invoked", just change “it” into “ignore,” like this:

    package org.scalatest.examples.flatspec.ignore
    
    import org.scalatest.SafeFlatSpec
    
    class SetSpec extends SafeFlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      ignore should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the first test and report that the second test was ignored:
    An empty Set
    - should have size 0
    - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    When using shorthand notation, you won't have an it to change into ignore for the first test of each new subject. To ignore such tests, you must instead change in to ignore. For example, to temporarily disable the test with the name "An empty Set should have size 0", change “in” into “ignore” like this:
    package org.scalatest.examples.flatspec.ignoreafter
    
    import org.scalatest.SafeFlatSpec
    
    class SetSpec extends SafeFlatSpec {
    
      "An empty Set" should "have size 0" ignore {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of StackSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    An empty Set
    - should have size 0 !!! IGNORED !!!
    - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.flatspec.ignoreall
    
    import org.scalatest._
    
    @Ignore
    class SetSpec extends SafeFlatSpec {
    
      "An empty Set" should "have size 0" in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    An empty Set
    - should have size 0 !!! IGNORED !!!
    - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to SafeFlatSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by SafeFlatSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a specification to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by SafeFlatSpec to pass such information to the reporter. Here's an example:

    package org.scalatest.examples.flatspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFlatSpec with GivenWhenThen {
    
      "A mutable Set" should "allow an element to be added" in {
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this SafeFlatSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    SetSpec:
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    SafeFlatSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example SafeFlatSpec that uses markup:

    package org.scalatest.examples.flatspec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFlatSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      "A mutable Set" should "allow an element to be added" in {
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        markup("This test finished with a **bold** statement!")
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.flatspec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFlatSpec {
    
      "A mutable Set" should "allow an element to be added" in {
    
        info("info is recorded")
        markup("markup is *also* recorded")
        note("notes are sent immediately")
        alert("alerts are also sent immediately")
    
        val set = mutable.Set.empty[String]
        set += "clarity"
        assert(set.size === 1)
        assert(set.contains("clarity"))
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    A mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
    - should allow an element to be added
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented. You can mark tests as pending in SafeFlatSpec like this:
    package org.scalatest.examples.flatspec.pending
    
    import org.scalatest._
    
    class SetSpec extends SafeFlatSpec {
    
      "An empty Set" should "have size 0" in (pending)
    
      it should "produce NoSuchElementException when head is invoked" in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of SafeFlatSpec with:
    scala> new SetSpec execute
    
    It will run both tests but report that An empty Set should have size 0 is pending. You'll see:
    An empty Set
    - should have size 0 (pending)
    - should produce NoSuchElementException when head is invoked
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a SafeFlatSpec:
     "The Scala language" must "add correctly" in {
        Given("two integers")
        When("they are added")
        Then("the result is the sum of the two numbers")
        pending
      }
      // ...
    
    Would yield the following output when run in the interpreter:
    The Scala language
    - must add correctly (pending)
      + Given two integers
      + When they are added
      + Then the result is the sum of the two numbers
    
    == Tagging tests == A SafeFlatSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a SafeFlatSpec, groups of tests can optionally be included and/or excluded. To tag a SafeFlatSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for SafeFlatSpecs like this:
    package org.scalatest.examples.flatspec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place SafeFlatSpec tests into groups like this:
    import org.scalatest.SafeFlatSpec
    
    class SetSpec extends SafeFlatSpec {
    
      behavior of "An empty Set"
    
      it should "have size 0" taggedAs(SlowTest) in {
        assert(Set.empty.size === 0)
      }
    
      it should "produce NoSuchElementException when head is invoked" taggedAs(SlowTest, DbTest) in {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a SafeFlatSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or a holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.flatspec.getfixture
    
    import org.scalatest.SafeFlatSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFlatSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      "Testing" should "be easy" in {
        val f = fixture
        f.builder.append("easy!")
        assert(f.builder.toString === "ScalaTest is easy!")
        assert(f.buffer.isEmpty)
        f.buffer += "sweet"
      }
    
      it should "be fun" in {
        val f = fixture
        f.builder.append("fun!")
        assert(f.builder.toString === "ScalaTest is fun!")
        assert(f.buffer.isEmpty)
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.flatspec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.SafeFlatSpec
    
    class ExampleSpec extends SafeFlatSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      // This test needs the StringBuilder fixture
      "Testing" should "be productive" in new Builder {
        builder.append("productive!")
        assert(builder.toString === "ScalaTest is productive!")
      }
    
      // This test needs the ListBuffer[String] fixture
      "Test code" should "be readable" in new Buffer {
        buffer += ("readable!")
        assert(buffer === List("ScalaTest", "is", "readable!"))
      }
    
      // This test needs both the StringBuilder and ListBuffer
      it should "be clear and concise" in new Builder with Buffer {
        builder.append("clear!")
        buffer += ("concise!")
        assert(builder.toString === "ScalaTest is clear!")
        assert(buffer === List("ScalaTest", "is", "concise!"))
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. That is to say, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and send that information to the reporter:
    package org.scalatest.examples.flatspec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends SafeFlatSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      "This test" should "succeed" in {
        assert(1 + 1 === 2)
      }
    
      it should "fail" in {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes [[org.scalatest.TestData TestData]] such as the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.flatspec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.SafeFlatSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends SafeFlatSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      // This test needs the file fixture
      "Testing" should "be productive" in withFile { (file, writer) =>
        writer.write("productive!")
        writer.flush()
        assert(file.length === 24)
      }
    
      // This test needs the database fixture
      "Test code" should "be readable" in withDatabase { db =>
        db.append("readable!")
        assert(db.toString === "ScalaTest is readable!")
      }
    
      // This test needs both the file and the database
      it should "be clear and concise" in withDatabase { db =>
        withFile { (file, writer) => // loan-fixture methods compose
          db.append("clear!")
          writer.write("concise!")
          writer.flush()
          assert(db.toString === "ScalaTest is clear!")
          assert(file.length === 21)
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.SafeFlatSpec and overriding withFixture(OneArgTest). Each test in a fixture.SafeFlatSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.flatspec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.SafeFlatSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" should "be easy" in { f =>
        f.writer.write("easy!")
        f.writer.flush()
        assert(f.file.length === 18)
      }
    
      it should "be fun" in { f =>
        f.writer.write("fun!")
        f.writer.flush()
        assert(f.file.length === 17)
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.SafeFlatSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.flatspec.beforeandafter
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFlatSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.flatspec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.flatspec.composingbeforeandaftereach
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFlatSpec with Builder with Buffer {
    
      "Testing" should "be easy" in {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      it should "be fun" in {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a SafeFlatSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any SafeFlatSpec that uses them, so that the tests they contain will be registered as tests in that SafeFlatSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your SafeFlatSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the SafeFlatSpec that uses them. If they are shared between different SafeFlatSpecs, however, you could also define them in a separate trait that is mixed into each SafeFlatSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: SafeFlatSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        it should "be non-empty" in {
          assert(!newStack.empty)
        }
    
        it should "return the top item on peek" in {
          assert(newStack.peek === lastItemAdded)
        }
    
        it should "not remove the top item on peek" in {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        it should "remove the top item on pop" in {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        it should "not be full" in {
          assert(!newStack.full)
        }
    
        it should "add to the top on push" in {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but SafeFlatSpec offers a DSL for the purpose, which looks like this:
    it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    it should behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    it should behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    it should behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends SafeFlatSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      "A Stack (when empty)" should "be empty" in {
        assert(emptyStack.empty)
      }
    
      it should "complain on peek" in {
        intercept[IllegalStateException] {
          emptyStack.peek
        }
      }
    
      it should "complain on pop" in {
        intercept[IllegalStateException] {
          emptyStack.pop
        }
      }
    
      "A Stack (with one item)" should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    
      it should behave like nonFullStack(stackWithOneItem)
    
      "A Stack (with one item less than capacity)" should behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
    
      it should behave like nonFullStack(stackWithOneItemLessThanCapacity)
    
      "A Stack (full)" should "be full" in {
        assert(fullStack.full)
      }
    
      it should behave like nonEmptyStack(fullStack, lastValuePushed)
    
      it should "complain on a push" in {
        intercept[IllegalStateException] {
          fullStack.push(10)
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new SharedTestExampleSpec execute
    A Stack (when empty)
    - should be empty
    - should complain on peek
    - should complain on pop
    A Stack (with one item)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (with one item less than capacity)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (full)
    - should be full
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a SafeFlatSpec is to make sure each invocation of a behavior function is in the context of a different set of when, verb (should, must, or can), and that clauses, which will prepend a string to each test name. For example, the following code in a SafeFlatSpec would register a test with the name "A Stack (when empty) should be empty":
      behavior of "A Stack (when empty)"
    
      it should "be empty" in {
        assert(emptyStack.empty)
      }
      // ...
    
    Or, using the shorthand notation:
      "A Stack" when {
        "empty" should {
          "be empty" in {
            assert(emptyStack.empty)
          }
        }
      }
      // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is in the context of a different combination of when, verb, and that clauses.

  90. trait SafeFlatSpecLike extends Suite with SafeTestRegistration with ShouldVerb with MustVerb with CanVerb with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class SafeFlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class SafeFlatSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    SafeFlatSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of SafeFlatSpec into some other class, you can use this trait instead, because class SafeFlatSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of SafeFlatSpec.

  91. class SafeFreeSpec extends SafeFreeSpecLike

    Permalink

    Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    Facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    SafeFreeSpec is so named because unlike classes such as WordSpec, FlatSpec, and FunSpec, it is enforces no structure on the text. You are free to compose text however you like. (A SafeFreeSpec is like free-verse poetry as opposed to a sonnet or haiku, which defines a structure for the text of the poem.)

    Recommended Usage: Because it gives absolute freedom (and no guidance) on how specification text should be written, SafeFreeSpec is a good choice for teams experienced with BDD and able to agree on how to structure the specification text.

    Here's an example SafeFreeSpec:

    package org.scalatest.examples.freespec
    
    import org.scalatest.SafeFreeSpec
    
    class SetSpec extends SafeFreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    

    In a SafeFreeSpec you write a test with a string followed by in and the body of the test in curly braces, like this:

    "should have size 0" in {
      // ...
    }
    

    You can nest a test inside any number of description clauses, which you write with a string followed by a dash character and a block, like this:

    "A Set" - {
      // ...
    }
    

    You can nest description clauses as deeply as you want. Because the description clause is denoted with an operator, not a word like should, you are free to structure the text however you wish. Here's an example:

    import org.scalatest.SafeFreeSpec
    
    class StackSpec extends SafeFreeSpec {
      "A Stack" - {
        "whenever it is empty" - {
          "certainly ought to" - {
            "be empty" in {
              // ...
            }
            "complain on peek" in {
              // ...
            }
            "complain on pop" in {
              // ...
            }
          }
        }
        "but when full, by contrast, must" - {
          "be full" in {
            // ...
          }
          "complain on push" in {
            // ...
          }
        }
      }
    }
    

    Running the above StackSpec in the interpreter would yield:

    scala> new StackSpec execute
    StackSpec:
    A Stack
      whenever it is empty
        certainly ought to
        - be empty
        - complain on peek
        - complain on pop
      but when full, by contrast, must
      - be full
      - complain on push
    

    A SafeFreeSpec can also be used to write a specification-style test in languages other than English. For example:

    import org.scalatest.SafeFreeSpec
    
    class ComputerRoomRulesSpec extends SafeFreeSpec {
      "Achtung!" - {
        "Alle touristen und non-technischen lookenpeepers!" - {
          "Das machine is nicht fuer fingerpoken und mittengrabben." in {
            // ...
          }
          "Is easy" - {
            "schnappen der springenwerk" in {
              // ...
            }
            "blowenfusen" in {
              // ...
            }
            "und poppencorken mit spitzen sparken." in {
              // ...
            }
          }
          "Das machine is diggen by experten only." in {
            // ...
          }
          "Is nicht fuer gerwerken by das dummkopfen." in {
            // ...
          }
          "Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets." in {
            // ...
          }
          "Relaxen und watchen das blinkenlights." in {
            // ...
          }
        }
      }
    }
    

    Running the above ComputerRoomRulesSpec in the interpreter would yield:

    scala> new ComputerRoomRulesSpec execute
    ComputerRoomRulesSpec:
    Achtung!
      Alle touristen und non-technischen lookenpeepers!
      - Das machine is nicht fuer fingerpoken und mittengrabben.
        Is easy
        - schnappen der springenwerk
        - blowenfusen
        - und poppencorken mit spitzen sparken.
      - Das machine is diggen by experten only.
      - Is nicht fuer gerwerken by das dummkopfen.
      - Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets.
      - Relaxen und watchen das blinkenlights.
    

    A SafeFreeSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered while the SafeFreeSpec is in its registration phase. Any attempt to register a test after the SafeFreeSpec has entered its ready phase, i.e., after run has been invoked on the SafeFreeSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using SafeFreeSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, SafeFreeSpec adds a method ignore to strings that can be used instead of in to register a test. For example, to temporarily disable the test with the name "A Stack should pop values in last-in-first-out order", just change “in” into “ignore,” like this:

    package org.scalatest.examples.freespec.ignore
    
    import org.scalatest.SafeFreeSpec
    
    class SetSpec extends SafeFreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" ignore {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.freespec.ignoreall
    
    import org.scalatest.SafeFreeSpec
    import org.scalatest.Ignore
    
    @Ignore
    class SetSpec extends SafeFreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to SafeFreeSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by SafeFreeSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event.

    One use case for the Informer is to pass more information about a specification to the reporter. For example, the GivenWhenThen trait provides methods that use the implicit info provided by SafeFreeSpec to pass such information to the reporter. Here's an example:

    package org.scalatest.examples.freespec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFreeSpec with GivenWhenThen {
    
      "A mutable Set" - {
        "should allow an element to be added" in {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          info("That's all folks!")
        }
      }
    }
    

    If you run this SafeFreeSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    SafeFreeSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example SafeFreeSpec that uses markup:

    package org.scalatest.examples.freespec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFreeSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      "A mutable Set" - {
        "should allow an element to be added" in {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.freespec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFreeSpec {
    
      "A mutable Set" - {
        "should allow an element to be added" in {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    scala> new SetSpec execute
    SetSpec:
     A mutable Set
       + notes are sent immediately
       + alerts are also sent immediately
     - should allow an element to be added
       + info is recorded
       + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality it is intended to test, has not yet been implemented. You can mark tests as pending in a SafeFreeSpec like this:
    package org.scalatest.examples.freespec.pending
    
    import org.scalatest._
    
    class SetSpec extends SafeFreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" in (pending)
    
          "should produce NoSuchElementException when head is invoked" in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run both tests but report that should have size 0 is pending. You'll see:
    A Set
      when empty
      - should have size 0 (pending)
      - should produce NoSuchElementException when head is invoked
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. For example, the following snippet in a SafeFreeSpec:
     "The Scala language" - {
        "should add correctly" in {
          Given("two integers")
          When("they are added")
          Then("the result is the sum of the two numbers")
          pending
        }
        // ...
    
    Would yield the following output when run in the interpreter:
    The Scala language
    - should add correctly (pending)
      + Given two integers
      + When they are added
      + Then the result is the sum of the two numbers
    
    == Tagging tests == A SafeFreeSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a SafeFreeSpec, groups of tests can optionally be included and/or excluded. To tag a SafeFreeSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for SafeFreeSpecs like this:
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could tag SafeFreeSpec tests like this:
    package org.scalatest.examples.freespec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    import org.scalatest.SafeFreeSpec
    
    class SetSpec extends SafeFreeSpec {
    
      "A Set" - {
        "when empty" - {
          "should have size 0" taggedAs(SlowTest) in {
            assert(Set.empty.size === 0)
          }
    
          "should produce NoSuchElementException when head is invoked" taggedAs(SlowTest, DbTest) in {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a SafeFreeSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.freespec.getfixture
    
    import org.scalatest.SafeFreeSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFreeSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      "Testing" - {
        "should be easy" in {
          val f = fixture
          f.builder.append("easy!")
          assert(f.builder.toString === "ScalaTest is easy!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        "should be fun" in {
          val f = fixture
          f.builder.append("fun!")
          assert(f.builder.toString === "ScalaTest is fun!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.freespec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.SafeFreeSpec
    
    class ExampleSpec extends SafeFreeSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      "Testing" - {
        // This test needs the StringBuilder fixture
        "should be productive" in new Builder {
          builder.append("productive!")
          assert(builder.toString === "ScalaTest is productive!")
        }
      }
    
      "Test code" - {
        // This test needs the ListBuffer[String] fixture
        "should be readable" in new Buffer {
          buffer += ("readable!")
          assert(buffer === List("ScalaTest", "is", "readable!"))
        }
    
        // This test needs both the StringBuilder and ListBuffer
        "should be clear and concise" in new Builder with Buffer {
          builder.append("clear!")
          buffer += ("concise!")
          assert(builder.toString === "ScalaTest is clear!")
          assert(buffer === List("ScalaTest", "is", "concise!"))
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.freespec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends SafeFreeSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      "This test" - {
        "should succeed" in {
          assert(1 + 1 === 2)
        }
    
        "should fail" in {
          assert(1 + 1 === 3)
        }
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.freespec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.SafeFreeSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends SafeFreeSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" - {
        // This test needs the file fixture
        "should be productive" in withFile { (file, writer) =>
          writer.write("productive!")
          writer.flush()
          assert(file.length === 24)
        }
      }
    
      "Test code" - {
        // This test needs the database fixture
        "should be readable" in withDatabase { db =>
          db.append("readable!")
          assert(db.toString === "ScalaTest is readable!")
        }
    
        // This test needs both the file and the database
        "should be clear and concise" in withDatabase { db =>
          withFile { (file, writer) => // loan-fixture methods compose
            db.append("clear!")
            writer.write("concise!")
            writer.flush()
            assert(db.toString === "ScalaTest is clear!")
            assert(file.length === 21)
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.SafeFreeSpec and overriding withFixture(OneArgTest). Each test in a fixture.SafeFreeSpec takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.freespec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.SafeFreeSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      "Testing" - {
        "should be easy" in { f =>
          f.writer.write("easy!")
          f.writer.flush()
          assert(f.file.length === 18)
        }
    
        "should be fun" in { f =>
          f.writer.write("fun!")
          f.writer.flush()
          assert(f.file.length === 17)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.SafeFreeSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.freespec.beforeandafter
    
    import org.scalatest.SafeFreeSpec
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFreeSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.freespec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFreeSpec with Builder with Buffer {
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.freespec.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFreeSpec with Builder with Buffer {
    
      "Testing" - {
        "should be easy" in {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        "should be fun" in {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a SafeFreeSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any SafeFreeSpec that uses them, so that the tests they contain will be registered as tests in that SafeFreeSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your SafeFreeSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the SafeFreeSpec that uses them. If they are shared between different SafeFreeSpecs, however, you could also define them in a separate trait that is mixed into each SafeFreeSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: SafeFreeSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        "be non-empty" in {
          assert(!newStack.empty)
        }
    
        "return the top item on peek" in {
          assert(newStack.peek === lastItemAdded)
        }
    
        "not remove the top item on peek" in {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        "remove the top item on pop" in {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        "not be full" in {
          assert(!newStack.full)
        }
    
        "add to the top on push" in {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but SafeFreeSpec offers a DSL for the purpose, which looks like this:
    behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends SafeFreeSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      "A Stack" - {
        "when empty" - {
          "should be empty" in {
            assert(emptyStack.empty)
          }
    
          "should complain on peek" in {
            intercept[IllegalStateException] {
              emptyStack.peek
            }
          }
    
          "should complain on pop" in {
            intercept[IllegalStateException] {
              emptyStack.pop
            }
          }
        }
    
        "when it contains one item" - {
          "should" - {
            behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
            behave like nonFullStack(stackWithOneItem)
          }
        }
    
        "when it contains one item less than capacity" - {
          "should" - {
            behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
            behave like nonFullStack(stackWithOneItemLessThanCapacity)
          }
        }
    
        "when full" - {
          "should be full" in {
            assert(fullStack.full)
          }
    
          "should" - {
            behave like nonEmptyStack(fullStack, lastValuePushed)
          }
    
          "should complain on a push" in {
            intercept[IllegalStateException] {
              fullStack.push(10)
            }
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new SharedTestExampleSpec execute
    SharedTestExampleSpec:
    A Stack
      when empty
      - should be empty
      - should complain on peek
      - should complain on pop
      when it contains one item
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
        - not be full
        - add to the top on push
      when it contains one item less than capacity
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
        - not be full
        - add to the top on push
      when full
      - should be full
        should
        - be non-empty
        - return the top item on peek
        - not remove the top item on peek
        - remove the top item on pop
      - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a SafeFreeSpec is to make sure each test is in the context of different surrounding description clauses, because a test's name is the concatenation of its surrounding clauses, followed by the test's text. For example, the following code in a SafeFreeSpec would register a test with the name "A Stack when empty should be empty":
    "A Stack" - {
      "when empty" - {
        "should be empty" in {
          assert(emptyStack.empty)
        }
      }
    }
    // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is in the context of a different surrounding description (dash) clauses.

  92. trait SafeFreeSpecLike extends Suite with SafeTestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class SafeFreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    Implementation trait for class SafeFreeSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are nested inside text clauses denoted with the dash operator (-).

    SafeFreeSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of SafeFreeSpec into some other class, you can use this trait instead, because class SafeFreeSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of SafeFreeSpec.

  93. class SafeFunSpec extends SafeFunSpecLike

    Permalink

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Recommended Usage: For teams coming from Ruby's RSpec tool, SafeFunSpec will feel familiar and comfortable; More generally, for any team that prefers BDD, SafeFunSpec's nesting and gentle guide to structuring text (with describe and it) provide an excellent general-purpose choice for writing specification-style tests.

    Here's an example SafeFunSpec:

    package org.scalatest.examples.funspec
    
    import org.scalatest.SafeFunSpec
    
    class SetSpec extends SafeFunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    

    A SafeFunSpec contains describe clauses and tests. You define a describe clause with describe, and a test with either it or they. describe, it, and and they are methods, defined in SafeFunSpec, which will be invoked by the primary constructor of SetSpec. A describe clause names, or gives more information about, the subject (class or other entity) you are specifying and testing. In the previous example, "A Set" is the subject under specification and test. With each test you provide a string (the spec text) that specifies one bit of behavior of the subject, and a block of code that tests that behavior. You place the spec text between the parentheses, followed by the test code between curly braces. The test code will be wrapped up as a function passed as a by-name parameter to it (or they), which will register the test for later execution.

    Note: the they method is intended for use when the subject is plural, for example:

    describe("The combinators") {
      they("should be easy to learn") {}
      they("should be efficient") {}
      they("should do something cool") {}
    }
    

    A SafeFunSpec's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered with the it or they methods while the SafeFunSpec is in its registration phase. Any attempt to register a test after the SafeFunSpec has entered its ready phase, i.e., after run has been invoked on the SafeFunSpec, will be met with a thrown TestRegistrationClosedException. The recommended style of using SafeFunSpec is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    When you execute a SafeFunSpec, it will send Formatters in the events it sends to the Reporter. ScalaTest's built-in reporters will report these events in such a way that the output is easy to read as an informal specification of the subject being tested. For example, were you to run SetSpec from within the Scala interpreter:

    scala> new SetSpec execute
    

    You would see:

    A Set
      when empty
      - should have size 0
      - should produce NoSuchElementException when head is invoked
    

    Or, to run just the “A Set when empty should have size 0” test, you could pass that test's name, or any unique substring of the name, such as "size 0" or even just "0". Here's an example:

    scala> new SetSuite execute "size 0"
    A Set
      when empty
      - should have size 0
    

    You can also pass to execute a config map of key-value pairs, which will be passed down into suites and tests, as well as other parameters that configure the run itself. For more information on running in the Scala interpreter, see the documentation for execute (below) and the ScalaTest shell.

    The execute method invokes a run method that takes two parameters. This run method, which actually executes the suite, will usually be invoked by a test runner, such as run, tools.Runner, a build tool, or an IDE.

    Note: SafeFunSpec's syntax is in great part inspired by RSpec, a Ruby BDD framework.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, SafeFunSpec provides registration methods that start with ignore instead of it or they. For example, to temporarily disable the test with the text "should have size 0", just change “it” into “ignore,” like this:

    package org.scalatest.examples.funspec.ignore
    
    import org.scalatest.SafeFunSpec
    
    class SetSpec extends SafeFunSpec {
    
      describe("A Set") {
        describe("when empty") {
          ignore("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run only the second test and report that the first test was ignored:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.funspec.ignoreall
    
    import org.scalatest.SafeFunSpec
    import org.scalatest.Ignore
    
    @Ignore
    class SetSpec extends SafeFunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSpec in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSpec in the Scala interpreter, you'll see:
    scala> new SetSpec execute
    SetSpec:
    A Set
      when empty
      - should have size 0 !!! IGNORED !!!
      - should produce NoSuchElementException when head is invoked !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to SafeFunSpec's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by SafeFunSpec's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via one of its apply methods. The Informer will then pass the information to the Reporter via an InfoProvided event. Here's an example in which the Informer returned by info is used implicitly by the Given, When, and Then methods of trait GivenWhenThen:

    package org.scalatest.examples.funspec.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFunSpec with GivenWhenThen {
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          info("That's all folks!")
        }
      }
    }
    

    If you run this SafeFunSpec from the interpreter, you will see the following output:

    scala> new SetSpec execute
    A mutable Set
    - should allow an element to be added
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks! 
    

    Documenters

    SafeFunSpec also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example SafeFunSpec that uses markup:

    package org.scalatest.examples.funspec.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFunSpec with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
          Given("an empty mutable Set")
          val set = mutable.Set.empty[String]
    
          When("an element is added")
          set += "clarity"
    
          Then("the Set should have size 1")
          assert(set.size === 1)
    
          And("the Set should contain the added element")
          assert(set.contains("clarity"))
    
          markup("This test finished with a **bold** statement!")
        }
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.funspec.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSpec extends SafeFunSpec {
    
      describe("A mutable Set") {
        it("should allow an element to be added") {
    
          info("info is recorded")
          markup("markup is *also* recorded")
          note("notes are sent immediately")
          alert("alerts are also sent immediately")
    
          val set = mutable.Set.empty[String]
          set += "clarity"
          assert(set.size === 1)
          assert(set.contains("clarity"))
        }
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSpec:
    A mutable Set
      + notes are sent immediately
      + alerts are also sent immediately
    - should allow an element to be added
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. You can mark a test as pending in SafeFunSpec by placing "(pending)" after the test name, like this:
    package org.scalatest.examples.funspec.pending
    
    import org.scalatest._
    
    class SetSpec extends SafeFunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0") (pending)
    
          it("should produce NoSuchElementException when head is invoked") {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of SetSpec with:
    scala> new SetSpec execute
    
    It will run both tests, but report that the test named "should have size 0" is pending. You'll see:
    A Set
      when empty
      - should have size 0 (pending)
      - should produce NoSuchElementException when head is invoked
    
    == Tagging tests == A SafeFunSpec's tests may be classified into groups by tagging them with string names. As with any suite, when executing a SafeFunSpec, groups of tests can optionally be included and/or excluded. To tag a SafeFunSpec's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for SafeFunSpecs like this:
    package org.scalatest.examples.funspec.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place SafeFunSpec tests into groups like this:
    import org.scalatest.SafeFunSpec
    
    class SetSpec extends SafeFunSpec {
    
      describe("A Set") {
        describe("when empty") {
          it("should have size 0", SlowTest) {
            assert(Set.empty.size === 0)
          }
    
          it("should produce NoSuchElementException when head is invoked", SlowTest, DbTest) {
            intercept[NoSuchElementException] {
              Set.empty.head
            }
          }
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a SafeFunSpec in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.funspec.getfixture
    
    import org.scalatest.SafeFunSpec
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFunSpec {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      describe("Testing") {
        it("should be easy") {
          val f = fixture
          f.builder.append("easy!")
          assert(f.builder.toString === "ScalaTest is easy!")
          assert(f.buffer.isEmpty)
          f.buffer += "sweet"
        }
    
        it("should be fun") {
          val f = fixture
          f.builder.append("fun!")
          assert(f.builder.toString === "ScalaTest is fun!")
          assert(f.buffer.isEmpty)
        }
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.funspec.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.SafeFunSpec
    
    class ExampleSpec extends SafeFunSpec {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      describe("Testing") {
        // This test needs the StringBuilder fixture
        it("should be productive") {
          new Builder {
            builder.append("productive!")
            assert(builder.toString === "ScalaTest is productive!")
          }
        }
      }
    
      describe("Test code") {
        // This test needs the ListBuffer[String] fixture
        it("should be readable") {
          new Buffer {
            buffer += ("readable!")
            assert(buffer === List("ScalaTest", "is", "readable!"))
          }
        }
    
        // This test needs both the StringBuilder and ListBuffer
        it("should be clear and concise") {
          new Builder with Buffer {
            builder.append("clear!")
            buffer += ("concise!")
            assert(builder.toString === "ScalaTest is clear!")
            assert(buffer === List("ScalaTest", "is", "concise!"))
          }
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.funspec.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSpec extends SafeFunSpec {
    
      override def withFixture(test: NoArgTest) = {
    
        try super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      describe("This test") {
        it("should succeed") {
          assert(1 + 1 === 2)
        }
    
        it("should fail") {
          assert(1 + 1 === 3)
        }
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    This test
    - should succeed
    - should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.funspec.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.SafeFunSpec
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSpec extends SafeFunSpec {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      describe("Testing") {
        // This test needs the file fixture
        it("should be productive") {
          withFile { (file, writer) =>
            writer.write("productive!")
            writer.flush()
            assert(file.length === 24)
          }
        }
      }
    
      describe("Test code") {
        // This test needs the database fixture
        it("should be readable") {
          withDatabase { db =>
            db.append("readable!")
            assert(db.toString === "ScalaTest is readable!")
          }
        }
    
        // This test needs both the file and the database
        it("should be clear and concise") {
          withDatabase { db =>
           withFile { (file, writer) => // loan-fixture methods compose
              db.append("clear!")
              writer.write("concise!")
              writer.flush()
              assert(db.toString === "ScalaTest is clear!")
              assert(file.length === 21)
            }
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.Suite and overriding withFixture(OneArgTest). Each test in a fixture.Suite takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.funspec.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSpec extends fixture.SafeFunSpec {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      describe("Testing") {
        it("should be easy") { f =>
          f.writer.write("easy!")
          f.writer.flush()
          assert(f.file.length === 18)
        }
    
        it("should be fun") { f =>
          f.writer.write("fun!")
          f.writer.flush()
          assert(f.file.length === 17)
        }
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.SafeFunSpec. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.funspec.beforeandafter
    
    import org.scalatest.SafeFunSpec
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSpec extends SafeFunSpec with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
        }
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.funspec.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFunSpec with Builder with Buffer {
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.funspec.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try super.afterEach() // To be stackable, must call super.afterEach
        finally buffer.clear()
      }
    }
    
    class ExampleSpec extends SafeFunSpec with Builder with Buffer {
    
      describe("Testing") {
        it("should be easy") {
          builder.append("easy!")
          assert(builder.toString === "ScalaTest is easy!")
          assert(buffer.isEmpty)
          buffer += "sweet"
        }
    
        it("should be fun") {
          builder.append("fun!")
          assert(builder.toString === "ScalaTest is fun!")
          assert(buffer.isEmpty)
          buffer += "clear"
        }
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a SafeFunSpec, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any SafeFunSpec that uses them, so that the tests they contain will be registered as tests in that SafeFunSpec. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your SafeFunSpec for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the SafeFunSpec that uses them. If they are shared between different SafeFunSpecs, however, you could also define them in a separate trait that is mixed into each SafeFunSpec that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    trait StackBehaviors { this: SafeFunSpec =>
    
      def nonEmptyStack(newStack: => Stack[Int], lastItemAdded: Int) {
    
        it("should be non-empty") {
          assert(!newStack.empty)
        }
    
        it("should return the top item on peek") {
          assert(newStack.peek === lastItemAdded)
        }
    
        it("should not remove the top item on peek") {
          val stack = newStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        it("should remove the top item on pop") {
          val stack = newStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(newStack: => Stack[Int]) {
    
        it("should not be full") {
          assert(!newStack.full)
        }
    
        it("should add to the top on push") {
          val stack = newStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but SafeFunSpec offers a DSL for the purpose, which looks like this:
    it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
    it should behave like nonFullStack(stackWithOneItem)
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    it should behave like nonEmptyStack // assuming lastValuePushed is also in scope inside nonEmptyStack
    it should behave like nonFullStack
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    class SharedTestExampleSpec extends SafeFunSpec with StackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      describe("A Stack") {
    
        describe("(when empty)") {
    
          it("should be empty") {
            assert(emptyStack.empty)
          }
    
          it("should complain on peek") {
            intercept[IllegalStateException] {
              emptyStack.peek
            }
          }
    
          it("should complain on pop") {
            intercept[IllegalStateException] {
              emptyStack.pop
            }
          }
        }
    
        describe("(with one item)") {
          it should behave like nonEmptyStack(stackWithOneItem, lastValuePushed)
          it should behave like nonFullStack(stackWithOneItem)
        }
    
        describe("(with one item less than capacity)") {
          it should behave like nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed)
          it should behave like nonFullStack(stackWithOneItemLessThanCapacity)
        }
    
        describe("(full)") {
    
          it("should be full") {
            assert(fullStack.full)
          }
    
          it should behave like nonEmptyStack(fullStack, lastValuePushed)
    
          it("should complain on a push") {
            intercept[IllegalStateException] {
              fullStack.push(10)
            }
          }
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new StackSpec execute
    A Stack (when empty)
    - should be empty
    - should complain on peek
    - should complain on pop
    A Stack (with one item)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (with one item less than capacity)
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should not be full
    - should add to the top on push
    A Stack (full)
    - should be full
    - should be non-empty
    - should return the top item on peek
    - should not remove the top item on peek
    - should remove the top item on pop
    - should complain on a push
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. A good way to solve this problem in a SafeFunSpec is to surround each invocation of a behavior function with a describe clause, which will prepend a string to each test name. For example, the following code in a SafeFunSpec would register a test with the name "A Stack (when empty) should be empty":
      describe("A Stack") {
    
        describe("(when empty)") {
    
          it("should be empty") {
            assert(emptyStack.empty)
          }
          // ...
    
    If the "should be empty" test was factored out into a behavior function, it could be called repeatedly so long as each invocation of the behavior function is inside a different set of describe clauses.

  94. trait SafeFunSpecLike extends Suite with SafeTestRegistration with Informing with Notifying with Alerting with Documenting

    Permalink

    Implementation trait for class SafeFunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    Implementation trait for class SafeFunSpec, which facilitates a “behavior-driven” style of development (BDD), in which tests are combined with text that specifies the behavior the tests verify.

    SafeFunSpec is a class, not a trait, to minimize compile time given there is a slight compiler overhead to mixing in traits compared to extending classes. If you need to mix the behavior of SafeFunSpec into some other class, you can use this trait instead, because class SafeFunSpec does nothing more than extend this trait and add a nice toString implementation.

    See the documentation of the class for a detailed overview of SafeFunSpec.

  95. class SafeFunSuite extends SafeFunSuiteLike

    Permalink

    A suite of tests in which each test is represented as a function value.

    A suite of tests in which each test is represented as a function value. The “Fun” in SafeFunSuite stands for “function.”

    Recommended Usage: For teams coming from xUnit, SafeFunSuite feels comfortable and familiar while still giving some benefits of BDD: SafeFunSuite makes it easy to write descriptive test names, natural to write focused tests, and generates specification-like output that can facilitate communication among stakeholders.

    Here's an example SafeFunSuite:

    package org.scalatest.examples.funsuite
    
    import org.scalatest.SafeFunSuite
    
    class SetSuite extends SafeFunSuite {
    
      test("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    

    test” is a method, defined in SafeFunSuite, which will be invoked by the primary constructor of SetSuite. You specify the name of the test as a string between the parentheses, and the test code itself between curly braces. The test code is a function passed as a by-name parameter to test, which registers it for later execution.

    A SafeFunSuite's lifecycle has two phases: the registration phase and the ready phase. It starts in registration phase and enters ready phase the first time run is called on it. It then remains in ready phase for the remainder of its lifetime.

    Tests can only be registered with the test method while the SafeFunSuite is in its registration phase. Any attempt to register a test after the SafeFunSuite has entered its ready phase, i.e., after run has been invoked on the SafeFunSuite, will be met with a thrown TestRegistrationClosedException. The recommended style of using SafeFunSuite is to register tests during object construction as is done in all the examples shown here. If you keep to the recommended style, you should never see a TestRegistrationClosedException.

    Note: SafeFunSuite was in part inspired by Rehersal, an early test framework for Scala.

    Ignored tests

    To support the common use case of temporarily disabling a test, with the good intention of resurrecting the test at a later time, SafeFunSuite provides registration methods that start with ignore instead of test. Here's an example: to temporarily

    package org.scalatest.examples.funsuite.ignore
    
    import org.scalatest.SafeFunSuite
    
    class SetSuite extends SafeFunSuite {
    
      ignore("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    If you run this version of SetSuite with:
    scala> new SetSuite execute
    
    It will run only the second test and report that the first test was ignored:
    SetSuite:
    - An empty Set should have size 0 !!! IGNORED !!!
    - Invoking head on an empty Set should produce NoSuchElementException
    
    If you wish to temporarily ignore an entire suite of tests, you can annotate the test class with @Ignore, like this:
    package org.scalatest.examples.funsuite.ignoreall
    
    import org.scalatest.SafeFunSuite
    import org.scalatest.Ignore
    
    @Ignore
    class SetSuite extends SafeFunSuite {
    
      test("An empty Set should have size 0") {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    When you mark a test class with a tag annotation, ScalaTest will mark each test defined in that class with that tag. Thus, marking the SetSuite in the above example with the @Ignore tag annotation means that both tests in the class will be ignored. If you run the above SetSuite in the Scala interpreter, you'll see:
    scala> new SetSuite execute
    SetSuite:
    - An empty Set should have size 0 !!! IGNORED !!!
    - Invoking head on an empty Set should produce NoSuchElementException !!! IGNORED !!!
    
    Note that marking a test class as ignored won't prevent it from being discovered by ScalaTest. Ignored classes will be discovered and run, and all their tests will be reported as ignored. This is intended to keep the ignored class visible, to encourage the developers to eventually fix and “un-ignore” it. If you want to prevent a class from being discovered at all, use the DoNotDiscover annotation instead. == Informers ==

    One of the parameters to SafeFunSuite's run method is a Reporter, which will collect and report information about the running suite of tests. Information about suites and tests that were run, whether tests succeeded or failed, and tests that were ignored will be passed to the Reporter as the suite runs. Most often the reporting done by default by SafeFunSuite's methods will be sufficient, but occasionally you may wish to provide custom information to the Reporter from a test. For this purpose, an Informer that will forward information to the current Reporter is provided via the info parameterless method. You can pass the extra information to the Informer via its apply method. The Informer will then pass the information to the Reporter via an InfoProvided event. Here's an example that shows both a direct use as well as an indirect use through the methods of GivenWhenThen:

    package org.scalatest.examples.funsuite.info
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends SafeFunSuite with GivenWhenThen {
    
      test("An element can be added to an empty mutable Set") {
    
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        info("That's all folks!")
      }
    }
    

    If you run this SafeFunSuite from the interpreter, you will see the following output:

    scala> new SetSuite execute
    SetSuite:
    - an element can be added to an empty mutable Set
      + Given an empty mutable Set
      + When an element is added
      + Then the Set should have size 1
      + And the Set should contain the added element
      + That's all folks!
    

    Documenters

    SafeFunSuite also provides a markup method that returns a Documenter, which allows you to send to the Reporter text formatted in Markdown syntax. You can pass the extra information to the Documenter via its apply method. The Documenter will then pass the information to the Reporter via an MarkupProvided event. Here's an example SafeFunSuite that uses markup:

    package org.scalatest.examples.funsuite.markup
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends SafeFunSuite with GivenWhenThen {
    
      markup { """
    
    Mutable Set
    -----------
    
    A set is a collection that contains no duplicate elements.
    
    To implement a concrete mutable set, you need to provide implementations
    of the following methods:
    
        def contains(elem: A): Boolean
        def iterator: Iterator[A]
        def += (elem: A): this.type
        def -= (elem: A): this.type
    
    If you wish that methods like `take`,
    `drop`, `filter` return the same kind of set,
    you should also override:
    
        def empty: This
    
    It is also good idea to override methods `foreach` and
    `size` for efficiency.
    
      """ }
    
      test("An element can be added to an empty mutable Set") {
    
        Given("an empty mutable Set")
        val set = mutable.Set.empty[String]
    
        When("an element is added")
        set += "clarity"
    
        Then("the Set should have size 1")
        assert(set.size === 1)
    
        And("the Set should contain the added element")
        assert(set.contains("clarity"))
    
        markup("This test finished with a **bold** statement!")
      }
    }
    
    Although all of ScalaTest's built-in reporters will display the markup text in some form, the HTML reporter will format the markup information into HTML. Thus, the main purpose of markup is to add nicely formatted text to HTML reports. Here's what the above SetSpec would look like in the HTML reporter: == Notifiers and alerters == ScalaTest records text passed to info and markup during tests, and sends the recorded text in the recordedEvents field of test completion events like TestSucceeded and TestFailed. This allows string reporters (like the standard out reporter) to show info and markup text after the test name in a color determined by the outcome of the test. For example, if the test fails, string reporters will show the info and markup text in red. If a test succeeds, string reporters will show the info and markup text in green. While this approach helps the readability of reports, it means that you can't use info to get status updates from long running tests. To get immediate (i.e., non-recorded) notifications from tests, you can use note (a Notifier) and alert (an Alerter). Here's an example showing the differences:
    package org.scalatest.examples.funsuite.note
    
    import collection.mutable
    import org.scalatest._
    
    class SetSuite extends SafeFunSuite {
    
      test("An element can be added to an empty mutable Set") {
    
        info("info is recorded")
        markup("markup is *also* recorded")
        note("notes are sent immediately")
        alert("alerts are also sent immediately")
    
        val set = mutable.Set.empty[String]
        set += "clarity"
        assert(set.size === 1)
        assert(set.contains("clarity"))
      }
    }
    
    Because note and alert information is sent immediately, it will appear before the test name in string reporters, and its color will be unrelated to the ultimate outcome of the test: note text will always appear in green, alert text will always appear in yellow. Here's an example:
    scala> new SetSpec execute
    SetSuite:
      + notes are sent immediately
      + alerts are also sent immediately
    - An element can be added to an empty mutable Set
      + info is recorded
      + markup is *also* recorded
    
    In summary, use info and markup for text that should form part of the specification output. Use note and alert to send status notifications. (Because the HTML reporter is intended to produce a readable, printable specification, info and markup text will appear in the HTML report, but note and alert text will not.) == Pending tests == A pending test is one that has been given a name but is not yet implemented. The purpose of pending tests is to facilitate a style of testing in which documentation of behavior is sketched out before tests are written to verify that behavior (and often, before the behavior of the system being tested is itself implemented). Such sketches form a kind of specification of what tests and functionality to implement later. To support this style of testing, a test can be given a name that specifies one bit of behavior required by the system being tested. The test can also include some code that sends more information about the behavior to the reporter when the tests run. At the end of the test, it can call method pending, which will cause it to complete abruptly with TestPendingException. Because tests in ScalaTest can be designated as pending with TestPendingException, both the test name and any information sent to the reporter when running the test can appear in the report of a test run. (In other words, the code of a pending test is executed just like any other test.) However, because the test completes abruptly with TestPendingException, the test will be reported as pending, to indicate the actual test, and possibly the functionality, has not yet been implemented. Although pending tests may be used more often in specification-style suites, such as org.scalatest.FunSpec, you can also use it in SafeFunSuite, like this:
    package org.scalatest.examples.funsuite.pending
    
    import org.scalatest._
    
    class SetSuite extends SafeFunSuite {
    
      test("An empty Set should have size 0") (pending)
    
      test("Invoking head on an empty Set should produce NoSuchElementException") {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    (Note: "(pending)" is the body of the test. Thus the test contains just one statement, an invocation of the pending method, which throws TestPendingException.) If you run this version of SetSuite with:
    scala> new SetSuite execute
    
    It will run both tests, but report that first test is pending. You'll see:
    SetSuite:
    - An empty Set should have size 0 (pending)
    - Invoking head on an empty Set should produce NoSuchElementException
    
    One difference between an ignored test and a pending one is that an ignored test is intended to be used during a significant refactorings of the code under test, when tests break and you don't want to spend the time to fix all of them immediately. You can mark some of those broken tests as ignored temporarily, so that you can focus the red bar on just failing tests you actually want to fix immediately. Later you can go back and fix the ignored tests. In other words, by ignoring some failing tests temporarily, you can more easily notice failed tests that you actually want to fix. By contrast, a pending test is intended to be used before a test and/or the code under test is written. Pending indicates you've decided to write a test for a bit of behavior, but either you haven't written the test yet, or have only written part of it, or perhaps you've written the test but don't want to implement the behavior it tests until after you've implemented a different bit of behavior you realized you need first. Thus ignored tests are designed to facilitate refactoring of existing code whereas pending tests are designed to facilitate the creation of new code. One other difference between ignored and pending tests is that ignored tests are implemented as a test tag that is excluded by default. Thus an ignored test is never executed. By contrast, a pending test is implemented as a test that throws TestPendingException (which is what calling the pending method does). Thus the body of pending tests are executed up until they throw TestPendingException. The reason for this difference is that it enables your unfinished test to send InfoProvided messages to the reporter before it completes abruptly with TestPendingException, as shown in the previous example on Informers that used the GivenWhenThen trait. == Tagging tests == A SafeFunSuite's tests may be classified into groups by tagging them with string names. As with any suite, when executing a SafeFunSuite, groups of tests can optionally be included and/or excluded. To tag a SafeFunSuite's tests, you pass objects that extend class org.scalatest.Tag to methods that register tests. Class Tag takes one parameter, a string name. If you have created tag annotation interfaces as described in the Tag documentation, then you will probably want to use tag names on your test functions that match. To do so, simply pass the fully qualified names of the tag interfaces to the Tag constructor. For example, if you've defined tag annotation interfaces with fully qualified names, com.mycompany.tags.SlowTest and com.mycompany.tags.DbTest, then you could create matching tags for SafeFunSuites like this:
    package org.scalatest.examples.funsuite.tagging
    
    import org.scalatest.Tag
    
    object SlowTest extends Tag("com.mycompany.tags.SlowTest")
    object DbTest extends Tag("com.mycompany.tags.DbTest")
    
    Given these definitions, you could place SafeFunSuite tests into groups like this:
    import org.scalatest.SafeFunSuite
    
    class SetSuite extends SafeFunSuite {
    
      test("An empty Set should have size 0", SlowTest) {
        assert(Set.empty.size === 0)
      }
    
      test("Invoking head on an empty Set should produce NoSuchElementException",
           SlowTest, DbTest) {
        intercept[NoSuchElementException] {
          Set.empty.head
        }
      }
    }
    
    This code marks both tests with the com.mycompany.tags.SlowTest tag, and the second test with the com.mycompany.tags.DbTest tag. The run method takes a Filter, whose constructor takes an optional Set[String] called tagsToInclude and a Set[String] called tagsToExclude. If tagsToInclude is None, all tests will be run except those those belonging to tags listed in the tagsToExclude Set. If tagsToInclude is defined, only tests belonging to tags mentioned in the tagsToInclude set, and not mentioned in tagsToExclude, will be run. It is recommended, though not required, that you create a corresponding tag annotation when you create a Tag object. A tag annotation allows you to tag all the tests of a SafeFunSuite in one stroke by annotating the class. For more information and examples, see the documentation for class Tag. == Shared fixtures == A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. ScalaTest recommends three techniques to eliminate such code duplication: - Refactor using Scala - Override withFixture - Mix in a before-and-after trait Each technique is geared towards helping you reduce code duplication without introducing instance vars, shared mutable objects, or other dependencies between tests. Eliminating shared mutable state across tests will make your test code easier to reason about and more amenable for parallel test execution. The following sections describe these techniques, including explaining the recommended usage for each. But first, here's a table summarizing the options:
    Refactor using Scala when different tests need different fixtures.
    get-fixture methods The extract method refactor helps you create a fresh instances of mutable fixture objects in each test that needs them, but doesn't help you clean them up when you're done.
    fixture-context objects By placing fixture methods and fields into traits, you can easily give each test just the newly created fixtures it needs by mixing together traits. Use this technique when you need different combinations of mutable fixture objects in different tests, and don't need to clean up after.
    loan-fixture methods Factor out dupicate code with the loan pattern when different tests need different fixtures that must be cleaned up afterwards.
    Override withFixture when most or all tests need the same fixture.
    withFixture(NoArgTest) The recommended default approach when most or all tests need the same fixture treatment. This general technique allows you, for example, to perform side effects at the beginning and end of all or most tests, transform the outcome of tests, retry tests, make decisions based on test names, tags, or other test data. Use this technique unless: - Different tests need different fixtures (refactor using Scala instead) - An exception in fixture code should abort the suite, not fail the test (use a before-and-after trait instead) - You have objects to pass into tests (override withFixture(OneArgTest) instead)
    withFixture(OneArgTest) Use when you want to pass the same fixture object or objects as a parameter into all or most tests.
    Mix in a before-and-after trait when you want an aborted suite, not a failed test, if the fixture code fails.
    BeforeAndAfter Use this boilerplate-buster when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    BeforeAndAfterEach Use when you want to stack traits that perform the same side-effects before and/or after tests, rather than at the beginning or end of tests.
    ==== Calling get-fixture methods ==== If you need to create the same mutable fixture objects in multiple tests, and don't need to clean them up after using them, the simplest approach is to write one or more get-fixture methods. A get-fixture method returns a new instance of a needed fixture object (or an holder object containing multiple fixture objects) each time it is called. You can call a get-fixture method at the beginning of each test that needs the fixture, storing the returned object or objects in local variables. Here's an example:
    package org.scalatest.examples.funsuite.getfixture
    
    import org.scalatest.SafeFunSuite
    import collection.mutable.ListBuffer
    
    class ExampleSuite extends SafeFunSuite {
    
      def fixture =
        new {
          val builder = new StringBuilder("ScalaTest is ")
          val buffer = new ListBuffer[String]
        }
    
      test("Testing should be easy") {
        val f = fixture
        f.builder.append("easy!")
        assert(f.builder.toString === "ScalaTest is easy!")
        assert(f.buffer.isEmpty)
        f.buffer += "sweet"
      }
    
      test("Testing should be fun") {
        val f = fixture
        f.builder.append("fun!")
        assert(f.builder.toString === "ScalaTest is fun!")
        assert(f.buffer.isEmpty)
      }
    }
    
    The “f.” in front of each use of a fixture object provides a visual indication of which objects are part of the fixture, but if you prefer, you can import the the members with “import f._” and use the names directly. If you need to configure fixture objects differently in different tests, you can pass configuration into the get-fixture method. For example, if you could pass in an initial value for a mutable fixture object as a parameter to the get-fixture method. ==== Instantiating fixture-context objects ==== An alternate technique that is especially useful when different tests need different combinations of fixture objects is to define the fixture objects as instance variables of fixture-context objects whose instantiation forms the body of tests. Like get-fixture methods, fixture-context objects are only appropriate if you don't need to clean up the fixtures after using them. To use this technique, you define instance variables intialized with fixture objects in traits and/or classes, then in each test instantiate an object that contains just the fixture objects needed by the test. Traits allow you to mix together just the fixture objects needed by each test, whereas classes allow you to pass data in via a constructor to configure the fixture objects. Here's an example in which fixture objects are partitioned into two traits and each test just mixes together the traits it needs:
    package org.scalatest.examples.funsuite.fixturecontext
    
    import collection.mutable.ListBuffer
    import org.scalatest.SafeFunSuite
    
    class ExampleSuite extends SafeFunSuite {
    
      trait Builder {
        val builder = new StringBuilder("ScalaTest is ")
      }
    
      trait Buffer {
        val buffer = ListBuffer("ScalaTest", "is")
      }
    
      // This test needs the StringBuilder fixture
      test("Testing should be productive") {
        new Builder {
          builder.append("productive!")
          assert(builder.toString === "ScalaTest is productive!")
        }
      }
    
      // This test needs the ListBuffer[String] fixture
      test("Test code should be readable") {
        new Buffer {
          buffer += ("readable!")
          assert(buffer === List("ScalaTest", "is", "readable!"))
        }
      }
    
      // This test needs both the StringBuilder and ListBuffer
      test("Test code should be clear and concise") {
        new Builder with Buffer {
          builder.append("clear!")
          buffer += ("concise!")
          assert(builder.toString === "ScalaTest is clear!")
          assert(buffer === List("ScalaTest", "is", "concise!"))
        }
      }
    }
    
    ==== Overriding withFixture(NoArgTest) ==== Although the get-fixture method and fixture-context object approaches take care of setting up a fixture at the beginning of each test, they don't address the problem of cleaning up a fixture at the end of the test. If you just need to perform a side-effect at the beginning or end of a test, and don't need to actually pass any fixture objects into the test, you can override withFixture(NoArgTest), one of ScalaTest's lifecycle methods defined in trait Suite. Trait Suite's implementation of runTest passes a no-arg test function to withFixture(NoArgTest). It is withFixture's responsibility to invoke that test function. Suite's implementation of withFixture simply invokes the function, like this:
    // Default implementation in trait Suite
    protected def withFixture(test: NoArgTest) = {
      test()
    }
    
    You can, therefore, override withFixture to perform setup before and/or cleanup after invoking the test function. If you have cleanup to perform, you should invoke the test function inside a try block and perform the cleanup in a finally clause, in case an exception propagates back through withFixture. (If a test fails because of an exception, the test function invoked by withFixture will result in a [[org.scalatest.Failed Failed]] wrapping the exception. Nevertheless, best practice is to perform cleanup in a finally clause just in case an exception occurs.) The withFixture method is designed to be stacked, and to enable this, you should always call the super implementation of withFixture, and let it invoke the test function rather than invoking the test function directly. In other words, instead of writing “test()”, you should write “super.withFixture(test)”, like this:
    // Your implementation
    override def withFixture(test: NoArgTest) = {
      // Perform setup
      try super.withFixture(test) // Invoke the test function
      finally {
        // Perform cleanup
      }
    }
    
    Here's an example in which withFixture(NoArgTest) is used to take a snapshot of the working directory if a test fails, and and send that information to the reporter:
    package org.scalatest.examples.funsuite.noargtest
    
    import java.io.File
    import org.scalatest._
    
    class ExampleSuite extends SafeFunSuite {
    
      override def withFixture(test: NoArgTest) = {
    
        super.withFixture(test) match {
          case failed: Failed =>
            val currDir = new File(".")
            val fileNames = currDir.list()
            info("Dir snapshot: " + fileNames.mkString(", "))
            failed
          case other => other
        }
      }
    
      test("This test should succeed") {
        assert(1 + 1 === 2)
      }
    
      test("This test should fail") {
        assert(1 + 1 === 3)
      }
    }
    
    Running this version of ExampleSuite in the interpreter in a directory with two files, hello.txt and world.txt would give the following output:
    scala> new ExampleSuite execute
    ExampleSuite:
    - this test should succeed
    - this test should fail *** FAILED ***
      2 did not equal 3 (:33)
      + Dir snapshot: hello.txt, world.txt 
    
    Note that the NoArgTest passed to withFixture, in addition to an apply method that executes the test, also includes the test name and the config map passed to runTest. Thus you can also use the test name and configuration objects in your withFixture implementation. ==== Calling loan-fixture methods ==== If you need to both pass a fixture object into a test and perform cleanup at the end of the test, you'll need to use the loan pattern. If different tests need different fixtures that require cleanup, you can implement the loan pattern directly by writing loan-fixture methods. A loan-fixture method takes a function whose body forms part or all of a test's code. It creates a fixture, passes it to the test code by invoking the function, then cleans up the fixture after the function returns. The following example shows three tests that use two fixtures, a database and a file. Both require cleanup after, so each is provided via a loan-fixture method. (In this example, the database is simulated with a StringBuffer.)
    package org.scalatest.examples.funsuite.loanfixture
    
    import java.util.concurrent.ConcurrentHashMap
    
    object DbServer { // Simulating a database server
      type Db = StringBuffer
      private val databases = new ConcurrentHashMap[String, Db]
      def createDb(name: String): Db = {
        val db = new StringBuffer
        databases.put(name, db)
        db
      }
      def removeDb(name: String) {
        databases.remove(name)
      }
    }
    
    import org.scalatest.SafeFunSuite
    import DbServer._
    import java.util.UUID.randomUUID
    import java.io._
    
    class ExampleSuite extends SafeFunSuite {
    
      def withDatabase(testCode: Db => Any) {
        val dbName = randomUUID.toString
        val db = createDb(dbName) // create the fixture
        try {
          db.append("ScalaTest is ") // perform setup
          testCode(db) // "loan" the fixture to the test
        }
        finally removeDb(dbName) // clean up the fixture
      }
    
      def withFile(testCode: (File, FileWriter) => Any) {
        val file = File.createTempFile("hello", "world") // create the fixture
        val writer = new FileWriter(file)
        try {
          writer.write("ScalaTest is ") // set up the fixture
          testCode(file, writer) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      // This test needs the file fixture
      test("Testing should be productive") {
        withFile { (file, writer) =>
          writer.write("productive!")
          writer.flush()
          assert(file.length === 24)
        }
      }
    
      // This test needs the database fixture
      test("Test code should be readable") {
        withDatabase { db =>
          db.append("readable!")
          assert(db.toString === "ScalaTest is readable!")
        }
      }
    
      // This test needs both the file and the database
      test("Test code should be clear and concise") {
        withDatabase { db =>
          withFile { (file, writer) => // loan-fixture methods compose
            db.append("clear!")
            writer.write("concise!")
            writer.flush()
            assert(db.toString === "ScalaTest is clear!")
            assert(file.length === 21)
          }
        }
      }
    }
    
    As demonstrated by the last test, loan-fixture methods compose. Not only do loan-fixture methods allow you to give each test the fixture it needs, they allow you to give a test multiple fixtures and clean everything up afterwards. Also demonstrated in this example is the technique of giving each test its own "fixture sandbox" to play in. When your fixtures involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is done in this example. This keeps tests completely isolated, allowing you to run them in parallel if desired. ==== Overriding withFixture(OneArgTest) ==== If all or most tests need the same fixture, you can avoid some of the boilerplate of the loan-fixture method approach by using a fixture.Suite and overriding withFixture(OneArgTest). Each test in a fixture.Suite takes a fixture as a parameter, allowing you to pass the fixture into the test. You must indicate the type of the fixture parameter by specifying FixtureParam, and implement a withFixture method that takes a OneArgTest. This withFixture method is responsible for invoking the one-arg test function, so you can perform fixture set up before, and clean up after, invoking and passing the fixture into the test function. To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let withFixture(NoArgTest) invoke the test function instead of invoking the test function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of writing “test(theFixture)”, you'd delegate responsibility for invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
    withFixture(test.toNoArgTest(theFixture))
    
    Here's a complete example:
    package org.scalatest.examples.funsuite.oneargtest
    
    import org.scalatest.fixture
    import java.io._
    
    class ExampleSuite extends fixture.SafeFunSuite {
    
      case class FixtureParam(file: File, writer: FileWriter)
    
      def withFixture(test: OneArgTest) = {
    
        // create the fixture
        val file = File.createTempFile("hello", "world")
        val writer = new FileWriter(file)
        val theFixture = FixtureParam(file, writer)
    
        try {
          writer.write("ScalaTest is ") // set up the fixture
          withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
        }
        finally writer.close() // clean up the fixture
      }
    
      test("Testing should be easy") { f =>
        f.writer.write("easy!")
        f.writer.flush()
        assert(f.file.length === 18)
      }
    
      test("Testing should be fun") { f =>
        f.writer.write("fun!")
        f.writer.flush()
        assert(f.file.length === 17)
      }
    }
    
    In this example, the tests actually required two fixture objects, a File and a FileWriter. In such situations you can simply define the FixtureParam type to be a tuple containing the objects, or as is done in this example, a case class containing the objects. For more information on the withFixture(OneArgTest) technique, see the documentation for fixture.SafeFunSuite. ==== Mixing in BeforeAndAfter ==== In all the shared fixture examples shown so far, the activities of creating, setting up, and cleaning up the fixture objects have been performed during the test. This means that if an exception occurs during any of these activities, it will be reported as a test failure. Sometimes, however, you may want setup to happen before the test starts, and cleanup after the test has completed, so that if an exception occurs during setup or cleanup, the entire suite aborts and no more tests are attempted. The simplest way to accomplish this in ScalaTest is to mix in trait BeforeAndAfter. With this trait you can denote a bit of code to run before each test with before and/or after each test each test with after, like this:
    package org.scalatest.examples.funsuite.beforeandafter
    
    import org.scalatest.SafeFunSuite
    import org.scalatest.BeforeAndAfter
    import collection.mutable.ListBuffer
    
    class ExampleSuite extends SafeFunSuite with BeforeAndAfter {
    
      val builder = new StringBuilder
      val buffer = new ListBuffer[String]
    
      before {
        builder.append("ScalaTest is ")
      }
    
      after {
        builder.clear()
        buffer.clear()
      }
    
      test("testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
      }
    }
    
    Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. If you mixed ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects. Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead, as shown later in the next section, composing fixtures by stacking traits. == Composing fixtures by stacking traits == In larger projects, teams often end up with several different fixtures that test classes need in different combinations, and possibly initialized (and cleaned up) in different orders. A good way to accomplish this in ScalaTest is to factor the individual fixtures into traits that can be composed using the stackable trait pattern. This can be done, for example, by placing withFixture methods in several traits, each of which call super.withFixture. Here's an example in which the StringBuilder and ListBuffer[String] fixtures used in the previous examples have been factored out into two stackable fixture traits named Builder and Buffer:
    package org.scalatest.examples.funsuite.composingwithfixture
    
    import org.scalatest._
    import collection.mutable.ListBuffer
    
    trait Builder extends SuiteMixin { this: Suite =>
    
      val builder = new StringBuilder
    
      abstract override def withFixture(test: NoArgTest) = {
        builder.append("ScalaTest is ")
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally builder.clear()
      }
    }
    
    trait Buffer extends SuiteMixin { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      abstract override def withFixture(test: NoArgTest) = {
        try super.withFixture(test) // To be stackable, must call super.withFixture
        finally buffer.clear()
      }
    }
    
    class ExampleSuite extends SafeFunSuite with Builder with Buffer {
    
      test("Testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("Testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    By mixing in both the Builder and Buffer traits, ExampleSuite gets both fixtures, which will be initialized before each test and cleaned up after. The order the traits are mixed together determines the order of execution. In this case, Builder is “super” to Buffer. If you wanted Buffer to be “super” to Builder, you need only switch the order you mix them together, like this:
    class Example2Suite extends Suite with Buffer with Builder
    
    And if you only need one fixture you mix in only that trait:
    class Example3Suite extends Suite with Builder
    
    Another way to create stackable fixture traits is by extending the BeforeAndAfterEach and/or BeforeAndAfterAll traits. BeforeAndAfterEach has a beforeEach method that will be run before each test (like JUnit's setUp), and an afterEach method that will be run after (like JUnit's tearDown). Similarly, BeforeAndAfterAll has a beforeAll method that will be run before all tests, and an afterAll method that will be run after all tests. Here's what the previously shown example would look like if it were rewritten to use the BeforeAndAfterEach methods instead of withFixture:
    package org.scalatest.examples.funsuite.composingbeforeandaftereach
    
    import org.scalatest._
    import org.scalatest.BeforeAndAfterEach
    import collection.mutable.ListBuffer
    
    trait Builder extends BeforeAndAfterEach { this: Suite =>
    
      val builder = new StringBuilder
    
      override def beforeEach() {
        builder.append("ScalaTest is ")
        super.beforeEach() // To be stackable, must call super.beforeEach
      }
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally builder.clear()
      }
    }
    
    trait Buffer extends BeforeAndAfterEach { this: Suite =>
    
      val buffer = new ListBuffer[String]
    
      override def afterEach() {
        try {
          super.afterEach() // To be stackable, must call super.afterEach
        }
        finally buffer.clear()
      }
    }
    
    class ExampleSuite extends SafeFunSuite with Builder with Buffer {
    
      test("Testing should be easy") {
        builder.append("easy!")
        assert(builder.toString === "ScalaTest is easy!")
        assert(buffer.isEmpty)
        buffer += "sweet"
      }
    
      test("Testing should be fun") {
        builder.append("fun!")
        assert(builder.toString === "ScalaTest is fun!")
        assert(buffer.isEmpty)
        buffer += "clear"
      }
    }
    
    To get the same ordering as withFixture, place your super.beforeEach call at the end of each beforeEach method, and the super.afterEach call at the beginning of each afterEach method, as shown in the previous example. It is a good idea to invoke super.afterEach in a try block and perform cleanup in a finally clause, as shown in the previous example, because this ensures the cleanup code is performed even if super.afterEach throws an exception. The difference between stacking traits that extend BeforeAndAfterEach versus traits that implement withFixture is that setup and cleanup code happens before and after the test in BeforeAndAfterEach, but at the beginning and end of the test in withFixture. Thus if a withFixture method completes abruptly with an exception, it is considered a failed test. By contrast, if any of the beforeEach or afterEach methods of BeforeAndAfterEach complete abruptly, it is considered an aborted suite, which will result in a SuiteAborted event. == Shared tests == Sometimes you may want to run the same test code on different fixture objects. In other words, you may want to write tests that are "shared" by different fixture objects. To accomplish this in a SafeFunSuite, you first place shared tests in behavior functions. These behavior functions will be invoked during the construction phase of any SafeFunSuite that uses them, so that the tests they contain will be registered as tests in that SafeFunSuite. For example, given this stack class:
    import scala.collection.mutable.ListBuffer
    
    class Stack[T] {
    
      val MAX = 10
      private val buf = new ListBuffer[T]
    
      def push(o: T) {
        if (!full)
          buf.prepend(o)
        else
          throw new IllegalStateException("can't push onto a full stack")
      }
    
      def pop(): T = {
        if (!empty)
          buf.remove(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def peek: T = {
        if (!empty)
          buf(0)
        else
          throw new IllegalStateException("can't pop an empty stack")
      }
    
      def full: Boolean = buf.size == MAX
      def empty: Boolean = buf.size == 0
      def size = buf.size
    
      override def toString = buf.mkString("Stack(", ", ", ")")
    }
    
    You may want to test the Stack class in different states: empty, full, with one item, with one item less than capacity, etc. You may find you have several tests that make sense any time the stack is non-empty. Thus you'd ideally want to run those same tests for three stack fixture objects: a full stack, a stack with a one item, and a stack with one item less than capacity. With shared tests, you can factor these tests out into a behavior function, into which you pass the stack fixture to use when running the tests. So in your SafeFunSuite for stack, you'd invoke the behavior function three times, passing in each of the three stack fixtures so that the shared tests are run for all three fixtures. You can define a behavior function that encapsulates these shared tests inside the SafeFunSuite that uses them. If they are shared between different SafeFunSuites, however, you could also define them in a separate trait that is mixed into each SafeFunSuite that uses them. For example, here the nonEmptyStack behavior function (in this case, a behavior method) is defined in a trait along with another method containing shared tests for non-full stacks:
    import org.scalatest.SafeFunSuite
    
    trait SafeFunSuiteStackBehaviors { this: SafeFunSuite =>
    
      def nonEmptyStack(createNonEmptyStack: => Stack[Int], lastItemAdded: Int) {
    
        test("empty is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          assert(!stack.empty)
        }
    
        test("peek is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          val size = stack.size
          assert(stack.peek === lastItemAdded)
          assert(stack.size === size)
        }
    
        test("pop is invoked on this non-empty stack: " + createNonEmptyStack.toString) {
          val stack = createNonEmptyStack
          val size = stack.size
          assert(stack.pop === lastItemAdded)
          assert(stack.size === size - 1)
        }
      }
    
      def nonFullStack(createNonFullStack: => Stack[Int]) {
    
        test("full is invoked on this non-full stack: " + createNonFullStack.toString) {
          val stack = createNonFullStack
          assert(!stack.full)
        }
    
        test("push is invoked on this non-full stack: " + createNonFullStack.toString) {
          val stack = createNonFullStack
          val size = stack.size
          stack.push(7)
          assert(stack.size === size + 1)
          assert(stack.peek === 7)
        }
      }
    }
    
    Given these behavior functions, you could invoke them directly, but SafeFunSuite offers a DSL for the purpose, which looks like this:
    testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    testsFor(nonFullStack(stackWithOneItem))
    
    If you prefer to use an imperative style to change fixtures, for example by mixing in BeforeAndAfterEach and reassigning a stack var in beforeEach, you could write your behavior functions in the context of that var, which means you wouldn't need to pass in the stack fixture because it would be in scope already inside the behavior function. In that case, your code would look like this:
    testsFor(nonEmptyStack) // assuming lastValuePushed is also in scope inside nonEmptyStack
    testsFor(nonFullStack)
    
    The recommended style, however, is the functional, pass-all-the-needed-values-in style. Here's an example:
    import org.scalatest.SafeFunSuite
    
    class StackSafeFunSuite extends SafeFunSuite with SafeFunSuiteStackBehaviors {
    
      // Stack fixture creation methods
      def emptyStack = new Stack[Int]
    
      def fullStack = {
        val stack = new Stack[Int]
        for (i <- 0 until stack.MAX)
          stack.push(i)
        stack
      }
    
      def stackWithOneItem = {
        val stack = new Stack[Int]
        stack.push(9)
        stack
      }
    
      def stackWithOneItemLessThanCapacity = {
        val stack = new Stack[Int]
        for (i <- 1 to 9)
          stack.push(i)
        stack
      }
    
      val lastValuePushed = 9
    
      test("empty is invoked on an empty stack") {
        val stack = emptyStack
        assert(stack.empty)
      }
    
      test("peek is invoked on an empty stack") {
        val stack = emptyStack
        intercept[IllegalStateException] {
          stack.peek
        }
      }
    
      test("pop is invoked on an empty stack") {
        val stack = emptyStack
        intercept[IllegalStateException] {
          emptyStack.pop
        }
      }
    
      testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
      testsFor(nonFullStack(stackWithOneItem))
    
      testsFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
      testsFor(nonFullStack(stackWithOneItemLessThanCapacity))
    
      test("full is invoked on a full stack") {
        val stack = fullStack
        assert(stack.full)
      }
    
      testsFor(nonEmptyStack(fullStack, lastValuePushed))
    
      test("push is invoked on a full stack") {
        val stack = fullStack
        intercept[IllegalStateException] {
          stack.push(10)
        }
      }
    }
    
    If you load these classes into the Scala interpreter (with scalatest's JAR file on the class path), and execute it, you'll see:
    scala> new StackSafeFunSuite execute
    StackSafeFunSuite:
    - empty is invoked on an empty stack
    - peek is invoked on an empty stack
    - pop is invoked on an empty stack
    - empty is invoked on this non-empty stack: Stack(9)
    - peek is invoked on this non-empty stack: Stack(9)
    - pop is invoked on this non-empty stack: Stack(9)
    - full is invoked on this non-full stack: Stack(9)
    - push is invoked on this non-full stack: Stack(9)
    - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - full is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - push is invoked on this non-full stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)
    - full is invoked on a full stack
    - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
    - push is invoked on a full stack
    
    One thing to keep in mind when using shared tests is that in ScalaTest, each test in a suite must have a unique name. If you register the same tests repeatedly in the same suite, one problem you may encounter is an exception at runtime complaining that multiple tests are being registered with the same test name. In a SafeFunSuite there is no nesting construct analogous to FunSpec's describe clause. Therefore, you need to do a bit of extra work to ensure that the test names are unique. If a duplicate test name problem shows up in a SafeFunSuite, you'll need to pass in a prefix or suffix string to add to each test name. You can pass this string the same way you pass any other data needed by the shared tests, or just call toString on the shared fixture object. This is the approach taken by the previous SafeFunSuiteStackBehaviors example. Given this SafeFunSuiteStackBehaviors trait, calling it with the stackWithOneItem fixture, like this:
    testsFor(nonEmptyStack(stackWithOneItem, lastValuePushed))
    
    yields test names: - empty is invoked on this non-empty stack: Stack(9) - peek is invoked on this non-empty stack: Stack(9) - pop is invoked on this non-empty stack: Stack(9) Whereas calling it with the stackWithOneItemLessThanCapacity fixture, like this:
    testsFor(nonEmptyStack(stackWithOneItemLessThanCapacity, lastValuePushed))
    
    yields different test names: - empty is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - peek is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1) - pop is invoked on this non-empty stack: Stack(9, 8, 7, 6, 5, 4, 3, 2, 1)