import org.scalatest.scalacheck.CheckSuite
 import org.scalacheck.Arbitrary._
 import org.scalacheck.Prop._

 class MySuite extends CheckSuite {
   def testConcat() {
     checkProperty(
       (a: List[Int], b: List[Int]) => {
         a.size + b.size == (a ::: b).size
       }
     )
   }
 }
 

The checkProperty method, defined in CheckSuite, makes it easy to write property-based tests inside ScalaTest, JUnit, and TestNG test suites. This example specifies a property that List's ::: method should obey. ScalaCheck properties are expressed as function values that take as parameters the required test data, which will be generated by ScalaCheck. In this case, the test data is composed of lists of integer named a and b. Inside the body of the function, you see:

 * a.size + b.size == (a ::: b).size
 

The property in this case is a Boolean expression that will yield true if the size of the concatenated list is equal to the size of each individual list added together. With this small amount of code, ScalaCheck will generate possibly hundreds of values for a and b and test each one, looking for a value for which the property doesn't hold. If the property holds true for every value ScalaCheck tries, checkProperty returns normally. Otherwise, checkProperty will complete abruptly with an AssertionError that contains information including the value that caused the failure.

For more information on using ScalaCheck properties, see the documentation for ScalaCheck, which is available from http://code.google.com/p/scalacheck/.

To execute CheckSuites with ScalaTest's Runner, you must include ScalaCheck's jar file on the class path or runpath. This version of CheckSuite was tested with ScalaCheck version 1.1.1.