org.scalatest.prop

Checkers

trait Checkers extends AnyRef

Trait that contains several “check” methods that perform ScalaCheck property checks. If ScalaCheck finds a test case for which a property doesn't hold, the problem will be reported as a ScalaTest test failure.

To use ScalaCheck, you specify properties and, in some cases, generators that generate test data. You need not always create generators, because ScalaCheck provides many default generators for you that can be used in many situations. ScalaCheck will use the generators to generate test data and with that data run tests that check that the property holds. Property-based tests can, therefore, give you a lot more testing for a lot less code than assertion-based tests. Here's an example of using ScalaCheck from a JUnitSuite:

import org.scalatest.junit.JUnitSuite
import org.scalatest.prop.Checkers
import org.scalacheck.Arbitrary._
import org.scalacheck.Prop._
class MySuite extends JUnitSuite with Checkers {
  @Test
  def testConcat() {
    check((a: List[Int], b: List[Int]) => a.size + b.size == (a ::: b).size)
  }
}

The check method, defined in Checkers, 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 the required test data as parameters. ScalaCheck will generate test data using generators and repeatedly pass generated data to the function. In this case, the test data is composed of integer lists 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 value pairs for a and b and test each pair, looking for a pair of integers for which the property doesn't hold. If the property holds true for every value ScalaCheck tries,check returns normally. Otherwise, check will complete abruptly with a TestFailedException that contains information about the failure, including the values that cause the property to be false.

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

To execute a suite that mixes in Checkers with ScalaTest's Runner, you must include ScalaCheck's jar file on the class path or runpath. This version of Checkers was tested with ScalaCheck version 1.1.1. This trait must be mixed into a ScalaTest Suite, because its self type is org.scalatest.Suite.

    authors:

  1. Bill Venners

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Value Members

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

  2. def !=(arg0: Any): Boolean

    o != arg0 is the same as !(o == (arg0)).

  3. def ##(): Int

  4. def $asInstanceOf[T0](): T0

  5. def $isInstanceOf[T0](): Boolean

  6. def ==(arg0: AnyRef): Boolean

    o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).

  7. def ==(arg0: Any): Boolean

    o == arg0 is the same as o.equals(arg0).

  8. def asInstanceOf[T0]: T0

    This method is used to cast the receiver object to be of type T0.

  9. def check(p: Prop): Unit

    Check a property.

  10. def check(p: Prop, prms: Params): Unit

    Check a property with the given testing parameters.

  11. def check[A1, A2, A3, A4, A5, A6, P](f: (A1, A2, A3, A4, A5, A6) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty, a3: Arbitrary[A3], s3: Shrink[A3], pp3: (A3) ⇒ Pretty, a4: Arbitrary[A4], s4: Shrink[A4], pp4: (A4) ⇒ Pretty, a5: Arbitrary[A5], s5: Shrink[A5], pp5: (A5) ⇒ Pretty, a6: Arbitrary[A6], s6: Shrink[A6], pp6: (A6) ⇒ Pretty): Unit

    Convert the passed 6-arg function into a property, and check it.

  12. def check[A1, A2, A3, A4, A5, P](f: (A1, A2, A3, A4, A5) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty, a3: Arbitrary[A3], s3: Shrink[A3], pp3: (A3) ⇒ Pretty, a4: Arbitrary[A4], s4: Shrink[A4], pp4: (A4) ⇒ Pretty, a5: Arbitrary[A5], s5: Shrink[A5], pp5: (A5) ⇒ Pretty): Unit

    Convert the passed 5-arg function into a property, and check it.

  13. def check[A1, A2, A3, A4, P](f: (A1, A2, A3, A4) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty, a3: Arbitrary[A3], s3: Shrink[A3], pp3: (A3) ⇒ Pretty, a4: Arbitrary[A4], s4: Shrink[A4], pp4: (A4) ⇒ Pretty): Unit

    Convert the passed 4-arg function into a property, and check it.

  14. def check[A1, A2, A3, P](f: (A1, A2, A3) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty, a3: Arbitrary[A3], s3: Shrink[A3], pp3: (A3) ⇒ Pretty): Unit

    Convert the passed 3-arg function into a property, and check it.

  15. def check[A1, A2, P](f: (A1, A2) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty): Unit

    Convert the passed 2-arg function into a property, and check it.

  16. def check[A1, P](f: (A1) ⇒ P)(implicit p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty): Unit

    Convert the passed 1-arg function into a property, and check it.

  17. def clone(): AnyRef

    This method creates and returns a copy of the receiver object.

  18. def eq(arg0: AnyRef): Boolean

    This method is used to test whether the argument (arg0) is a reference to the receiver object (this).

  19. def equals(arg0: Any): Boolean

    This method is used to compare the receiver object (this) with the argument object (arg0) for equivalence.

  20. def finalize(): Unit

    This method is called by the garbage collector on the receiver object when garbage collection determines that there are no more references to the object.

  21. def getClass(): java.lang.Class[_ <: java.lang.Object]

    Returns a representation that corresponds to the dynamic class of the receiver object.

  22. def hashCode(): Int

    Returns a hash code value for the object.

  23. def isInstanceOf[T0]: Boolean

    This method is used to test whether the dynamic type of the receiver object is T0.

  24. def ne(arg0: AnyRef): Boolean

    o.ne(arg0) is the same as !(o.eq(arg0)).

  25. def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

  26. def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

  27. def synchronized[T0](arg0: T0): T0

  28. def toString(): String

    Returns a string representation of the object.

  29. def wait(): Unit

  30. def wait(arg0: Long, arg1: Int): Unit

  31. def wait(arg0: Long): Unit