org.scalatest.matchers

BePropertyMatcher

trait BePropertyMatcher [-T] extends (T) ⇒ BePropertyMatchResult

Trait extended by matcher objects, which may appear after the word be, that can match against a Boolean property. The match will succeed if and only if the Boolean property equals true. The object containing the property, which must be of the type specified by the BePropertyMatcher's type parameter T, is passed to the BePropertyMatcher's apply method. The result is a BePropertyMatchResult. A BePropertyMatcher is, therefore, a function from the specified type, T, to a BePropertyMatchResult.

Although BePropertyMatcher and Matcher represent similar concepts, they have no inheritance relationship because Matcher is intended for use right after should or must whereas BePropertyMatcher is intended for use right after be.

A BePropertyMatcher essentially allows you to write statically typed Boolean property assertions similar to the dynamic ones that use symbols:

tempFile should be a ('file) // dynamic: uses reflection
tempFile should be a (file)  // type safe: only works on Files; no reflection used

One good way to organize custom matchers is to place them inside one or more traits that you can then mix into the suites or specs that need them. Here's an example that includes two BePropertyMatchers:

trait CustomMatchers {

  class FileBePropertyMatcher extends BePropertyMatcher[java.io.File] {
    def apply(left: java.io.File) = BePropertyMatchResult(left.isFile, "file")
  }

  class DirectoryBePropertyMatcher extends BePropertyMatcher[java.io.File] {
    def apply(left: java.io.File) = BePropertyMatchResult(left.isDirectory, "directory")
  }

  val file = new FileBePropertyMatcher
  val directory = new DirectoryBePropertyMatcher
}

Because the type parameter of these two BePropertyMatchers is java.io.File, they can only be used with instances of that type. (The compiler will enforce this.) All they do is create a BePropertyMatchResult whose matches field is true if and only if the Boolean property is true. The second field, propertyName, is simply the string name of the property. The file and directory vals create variables that can be used in matcher expressions that test whether a java.io.File is a file or a directory. Here's an example:

class ExampleSpec extends Spec with ShouldMatchers with CustomMatchers {

  describe("A temp file") {

    it("should be a file, not a directory") {

      val tempFile = java.io.File.createTempFile("delete", "me")

      try {
        tempFile should be a (file)
        tempFile should not be a (directory)
      }
      finally {
        tempFile.delete()
      }
    }
  }
}

These matches should succeed, but if for example the first match, tempFile should be a (file), were to fail, you would get an error message like:

/tmp/delme1234me was not a file

For more information on BePropertyMatchResult and the meaning of its fields, please see the documentation for BePropertyMatchResult. To understand why BePropertyMatcher is contravariant in its type parameter, see the section entitled "Matcher's variance" in the documentation for Matcher.

Self Type
BePropertyMatcher[T]
Linear Supertypes
(T) ⇒ BePropertyMatchResult, AnyRef, Any
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Abstract Value Members

  1. def apply (objectWithProperty: T): BePropertyMatchResult

    Check to see if a Boolean property on the specified object, objectWithProperty, matches its expected value, and report the result in the returned BePropertyMatchResult.

    Check to see if a Boolean property on the specified object, objectWithProperty, matches its expected value, and report the result in the returned BePropertyMatchResult. The objectWithProperty is usually the value to the left of a should or must invocation. For example, tempFile would be passed as the objectWithProperty in:

    tempFile should be a (file)
    

    objectWithProperty

    the object with the Boolean property against which to match

    returns

    the BePropertyMatchResult that represents the result of the match

    Attributes
    abstract
    Definition Classes
    BePropertyMatcher → Function1

Concrete Value Members

  1. def != (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  2. def != (arg0: Any): Boolean

    Attributes
    final
    Definition Classes
    Any
  3. def ## (): Int

    Attributes
    final
    Definition Classes
    AnyRef → Any
  4. def == (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  5. def == (arg0: Any): Boolean

    Attributes
    final
    Definition Classes
    Any
  6. def andThen [A] (g: (BePropertyMatchResult) ⇒ A): (T) ⇒ A

    Definition Classes
    Function1
  7. def asInstanceOf [T0] : T0

    Attributes
    final
    Definition Classes
    Any
  8. def clone (): AnyRef

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  9. def compose [U] (g: (U) ⇒ T): BePropertyMatcher[U]

    Compose this BePropertyMatcher with the passed function, returning a new BePropertyMatcher.

    Compose this BePropertyMatcher with the passed function, returning a new BePropertyMatcher.

    This method overrides compose on Function1 to return a more specific function type of BePropertyMatcher.

    Definition Classes
    BePropertyMatcher → Function1
  10. def eq (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  11. def equals (arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  12. def finalize (): Unit

    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()
  13. def getClass (): java.lang.Class[_]

    Attributes
    final
    Definition Classes
    AnyRef
  14. def hashCode (): Int

    Definition Classes
    AnyRef → Any
  15. def isInstanceOf [T0] : Boolean

    Attributes
    final
    Definition Classes
    Any
  16. def ne (arg0: AnyRef): Boolean

    Attributes
    final
    Definition Classes
    AnyRef
  17. def notify (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
  18. def notifyAll (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
  19. def synchronized [T0] (arg0: ⇒ T0): T0

    Attributes
    final
    Definition Classes
    AnyRef
  20. def toString (): String

    Definition Classes
    Function1 → AnyRef → Any
  21. def wait (): Unit

    Attributes
    final
    Definition Classes
    AnyRef
    Annotations
    @throws()
  22. def wait (arg0: Long, arg1: Int): Unit

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    final
    Definition Classes
    AnyRef
    Annotations
    @throws()
  23. def wait (arg0: Long): Unit

    Attributes
    final
    Definition Classes
    AnyRef
    Annotations
    @throws()

Inherited from (T) ⇒ BePropertyMatchResult

Inherited from AnyRef

Inherited from Any