Checkers

Companion object Checkers

trait Checkers extends Configuration

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.

Property check configuration

The property checks performed by the check methods of this trait can be flexibly configured via the services provided by supertrait Configuration. The five configuration parameters for property checks along with their default values and meanings are described in the following table:

Configuration Parameter	Default Value	Meaning
minSuccessful	100	the minimum number of successful property evaluations required for the property to pass
maxDiscarded	500	the maximum number of discarded property evaluations allowed during a property check
minSize	0	the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists)
maxSize	100	the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists)
workers	1	specifies the number of worker threads to use during property evaluation

The check methods of trait Checkers each take a PropertyCheckConfiguration object as an implicit parameter. This object provides values for each of the five configuration parameters. Trait Configuration provides an implicit val named generatorDrivenConfig with each configuration parameter set to its default value. If you want to set one or more configuration parameters to a different value for all property checks in a suite you can override this val (or hide it, for example, if you are importing the members of the Checkers companion object rather than mixing in the trait.) For example, if you want all parameters at their defaults except for minSize and maxSize, you can override generatorDrivenConfig, like this:

implicit override val generatorDrivenConfig =
  PropertyCheckConfiguration(minSize = 10, sizeRange = 10)

Or, if hide it by declaring a variable of the same name in whatever scope you want the changed values to be in effect:

implicit val generatorDrivenConfig =
  PropertyCheckConfiguration(minSize = 10, sizeRange = 10)

In addition to taking a PropertyCheckConfiguration object as an implicit parameter, the check methods of trait Checkers also take a variable length argument list of PropertyCheckConfigParam objects that you can use to override the values provided by the implicit PropertyCheckConfiguration for a single check invocation. You place these configuration settings after the property or property function, For example, if you want to set minSuccessful to 500 for just one particular check invocation, you can do so like this:

check((n: Int) => n + 0 == n, minSuccessful(500))

This invocation of check will use 500 for minSuccessful and whatever values are specified by the implicitly passed PropertyCheckConfiguration object for the other configuration parameters. If you want to set multiple configuration parameters in this way, just list them separated by commas:

check((n: Int) => n + 0 == n, minSuccessful(500), maxDiscardedFactor(0.6))

The previous configuration approach works the same in Checkers as it does in GeneratorDrivenPropertyChecks. Trait Checkers also provides one check method that takes an org.scalacheck.Test.Parameters object, in case you want to configure ScalaCheck that way.

import org.scalacheck.Prop
import org.scalacheck.Test.Parameters
import org.scalatest.prop.Checkers._

check(Prop.forAll((n: Int) => n + 0 == n), Parameters.Default { override val minSuccessfulTests = 5 })

For more information, see the documentation for supertrait Configuration.

Source: Checkers.scala

Linear Supertypes

Configuration, AnyRef, Any

Known Subclasses

Checkers

Ordering

Alphabetic
By Inheritance

Inherited

Checkers
Configuration
AnyRef
Any

Hide All
Show All

Visibility

Public
All

Type Members

case class MaxDiscardedFactor(value: PosZDouble) extends PropertyCheckConfigParam with Product with Serializable

Definition Classes
Configuration
case class MinSize(value: PosZInt) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that specifies the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
A PropertyCheckConfigParam that specifies the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).

Definition Classes
Configuration
Exceptions thrown
IllegalArgumentException if specified value is less than zero.
case class MinSuccessful(value: PosInt) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that specifies the minimum number of successful property evaluations required for the property to pass.
A PropertyCheckConfigParam that specifies the minimum number of successful property evaluations required for the property to pass.

Definition Classes
Configuration
sealed abstract class PropertyCheckConfigParam extends Product with Serializable
Abstract class defining a family of configuration parameters for property checks.
Abstract class defining a family of configuration parameters for property checks.
The subclasses of this abstract class are used to pass configuration information to the forAll methods of traits PropertyChecks (for ScalaTest-style property checks) and Checkers(for ScalaCheck-style property checks).

Definition Classes
Configuration
case class PropertyCheckConfiguration(minSuccessful: PosInt = PosInt(10), maxDiscardedFactor: PosZDouble = PosZDouble(5.0), minSize: PosZInt = PosZInt(0), sizeRange: PosZInt = PosZInt(100), workers: PosInt = PosInt(1)) extends PropertyCheckConfigurable with Product with Serializable

Definition Classes
Configuration
case class SizeRange(value: PosZInt) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that (with minSize) specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
A PropertyCheckConfigParam that (with minSize) specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Note that the size range is added to minSize in order to calculate the maximum size passed to ScalaCheck. Using a range allows compile-time checking of a non-negative number being specified.

Definition Classes
Configuration
case class Workers(value: PosInt) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that specifies the number of worker threads to use when evaluating a property.
A PropertyCheckConfigParam that specifies the number of worker threads to use when evaluating a property.

Definition Classes
Configuration
Exceptions thrown
IllegalArgumentException if specified value is less than or equal to zero.
case class MaxDiscarded(value: Int) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that specifies the maximum number of discarded property evaluations allowed during property evaluation.
A PropertyCheckConfigParam that specifies the maximum number of discarded property evaluations allowed during property evaluation.
In GeneratorDrivenPropertyChecks, a property evaluation is discarded if it throws DiscardedEvaluationException, which is produce by whenever clause that evaluates to false. For example, consider this ScalaTest property check:
```
// forAll defined in GeneratorDrivenPropertyChecks
forAll { (n: Int) =>
  whenever (n > 0) {
    doubleIt(n) should equal (n * 2)
  }
}
```
In the above code, whenever a non-positive n is passed, the property function will complete abruptly with DiscardedEvaluationException.
Similarly, in Checkers, a property evaluation is discarded if the expression to the left of ScalaCheck's ==> operator is false. Here's an example:
```
// forAll defined in Checkers
forAll { (n: Int) =>
  (n > 0) ==> doubleIt(n) == (n * 2)
}
```
For either kind of property check, MaxDiscarded indicates the maximum number of discarded evaluations that will be allowed. As soon as one past this number of evaluations indicates it needs to be discarded, the property check will fail.
Definition Classes
Configuration
Annotations
@deprecated
Deprecated
Exceptions thrown
IllegalArgumentException if specified value is less than zero.
case class MaxSize(value: Int) extends PropertyCheckConfigParam with Product with Serializable
A PropertyCheckConfigParam that specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
A PropertyCheckConfigParam that specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Note that the maximum size should be greater than or equal to the minimum size. This requirement is enforced by the PropertyCheckConfig constructor and the forAll methods of traits PropertyChecks and Checkers. In other words, it is enforced at the point both a maximum and minimum size are provided together.

Definition Classes
Configuration
Annotations
@deprecated
Deprecated
use SizeRange instead
Exceptions thrown
IllegalArgumentException if specified value is less than zero.
case class PropertyCheckConfig(minSuccessful: Int = 10, maxDiscarded: Int = 500, minSize: Int = 0, maxSize: Int = 100, workers: Int = 1) extends PropertyCheckConfigurable with Product with Serializable
Configuration object for property checks.
Configuration object for property checks.
The default values for the parameters are:

minSuccessful 100

maxDiscarded 500

minSize 0

maxSize 100

workers 1

minSuccessful
the minimum number of successful property evaluations required for the property to pass.
maxDiscarded
the maximum number of discarded property evaluations allowed during a property check
minSize
the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
maxSize
the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
workers
specifies the number of worker threads to use during property evaluation

Definition Classes
Configuration
Annotations
@deprecated
Deprecated
Use PropertyCheckConfiguration instead
Exceptions thrown
IllegalArgumentException if the specified minSuccessful value is less than or equal to zero, the specified maxDiscarded value is less than zero, the specified minSize value is less than zero, the specified maxSize value is less than zero, the specified minSize is greater than the specified or default value of maxSize, or the specified workers value is less than or equal to zero.
trait PropertyCheckConfigurable extends AnyRef

Definition Classes
Configuration
Annotations
@deprecated
Deprecated
Use PropertyCheckConfiguration directly instead.

Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def ##(): Int

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

Definition Classes
AnyRef → Any
implicit def PropertyCheckConfig2PropertyCheckConfiguration(p: PropertyCheckConfig): PropertyCheckConfiguration
Implicitly converts PropertyCheckConfigs to PropertyCheckConfiguration, which enables a smoother upgrade path.
Implicitly converts PropertyCheckConfigs to PropertyCheckConfiguration, which enables a smoother upgrade path.

Definition Classes
Configuration
final def asInstanceOf[T0]: T0

Definition Classes
Any
def check[ASSERTION](p: Prop, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Check a property.
Check a property.
p
the property to check

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[ASSERTION](p: Prop, prms: Parameters)(implicit asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Check a property with the given testing parameters.
Check a property with the given testing parameters.
p
the property to check
prms
the test parameters

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, A2, A3, A4, A5, A6, P, ASSERTION](f: (A1, A2, A3, A4, A5, A6) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, 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, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 6-arg function into a property, and check it.
Convert the passed 6-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, A2, A3, A4, A5, P, ASSERTION](f: (A1, A2, A3, A4, A5) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, 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, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 5-arg function into a property, and check it.
Convert the passed 5-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, A2, A3, A4, P, ASSERTION](f: (A1, A2, A3, A4) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, 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, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 4-arg function into a property, and check it.
Convert the passed 4-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, A2, A3, P, ASSERTION](f: (A1, A2, A3) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, 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, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 3-arg function into a property, and check it.
Convert the passed 3-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, A2, P, ASSERTION](f: (A1, A2) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, a2: Arbitrary[A2], s2: Shrink[A2], pp2: (A2) ⇒ Pretty, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 2-arg function into a property, and check it.
Convert the passed 2-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def check[A1, P, ASSERTION](f: (A1) ⇒ P, configParams: PropertyCheckConfigParam*)(implicit config: PropertyCheckConfigurable, p: (P) ⇒ Prop, a1: Arbitrary[A1], s1: Shrink[A1], pp1: (A1) ⇒ Pretty, asserting: CheckerAsserting[ASSERTION], prettifier: Prettifier, pos: Position): Result
Convert the passed 1-arg function into a property, and check it.
Convert the passed 1-arg function into a property, and check it.
f
the function to be converted into a property and checked

Exceptions thrown
TestFailedException if a test case is discovered for which the property doesn't hold.
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@native() @throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
implicit val generatorDrivenConfig: PropertyCheckConfiguration
Implicit PropertyCheckConfig value providing default configuration values.
Implicit PropertyCheckConfig value providing default configuration values.

Definition Classes
Configuration
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
Annotations
@native()
def hashCode(): Int

Definition Classes
AnyRef → Any
Annotations
@native()
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def maxDiscardedFactor(value: PosZDouble): MaxDiscardedFactor
Returns a MaxDiscardedFactor property check configuration parameter containing the passed value, which specifies the factor of discarded property evaluations allowed during property evaluation.
Returns a MaxDiscardedFactor property check configuration parameter containing the passed value, which specifies the factor of discarded property evaluations allowed during property evaluation.

Definition Classes
Configuration
def minSize(value: PosZInt): MinSize
Returns a MinSize property check configuration parameter containing the passed value, which specifies the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Returns a MinSize property check configuration parameter containing the passed value, which specifies the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).

Definition Classes
Configuration
def minSuccessful(value: PosInt): MinSuccessful
Returns a MinSuccessful property check configuration parameter containing the passed value, which specifies the minimum number of successful property evaluations required for the property to pass.
Returns a MinSuccessful property check configuration parameter containing the passed value, which specifies the minimum number of successful property evaluations required for the property to pass.

Definition Classes
Configuration
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
Annotations
@native()
final def notifyAll(): Unit

Definition Classes
AnyRef
Annotations
@native()
def sizeRange(value: PosZInt): SizeRange
Returns a SizeRange property check configuration parameter containing the passed value, that (with minSize) specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Returns a SizeRange property check configuration parameter containing the passed value, that (with minSize) specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Note that the size range is added to minSize in order to calculate the maximum size passed to ScalaCheck. Using a range allows compile-time checking of a non-negative number being specified.

Definition Classes
Configuration
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
final def wait(): Unit

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

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

Definition Classes
AnyRef
Annotations
@native() @throws( ... )
def workers(value: PosInt): Workers
Returns a Workers property check configuration parameter containing the passed value, which specifies the number of worker threads to use when evaluating a property.
Returns a Workers property check configuration parameter containing the passed value, which specifies the number of worker threads to use when evaluating a property.

Definition Classes
Configuration
object PropertyCheckConfiguration extends Serializable

Definition Classes
Configuration

Deprecated Value Members

def maxDiscarded(value: Int): MaxDiscarded
Returns a MaxDiscarded property check configuration parameter containing the passed value, which specifies the maximum number of discarded property evaluations allowed during property evaluation.
Returns a MaxDiscarded property check configuration parameter containing the passed value, which specifies the maximum number of discarded property evaluations allowed during property evaluation.

Definition Classes
Configuration
Annotations
@deprecated
Deprecated
use maxDiscardedFactor instead
Exceptions thrown
IllegalArgumentException if specified value is less than zero.
def maxSize(value: Int): MaxSize
Returns a MaxSize property check configuration parameter containing the passed value, which specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Returns a MaxSize property check configuration parameter containing the passed value, which specifies the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
Note that the maximum size should be greater than or equal to the minimum size. This requirement is enforced by the PropertyCheckConfig constructor and the forAll methods of traits PropertyChecks and Checkers. In other words, it is enforced at the point both a maximum and minimum size are provided together.

Definition Classes
Configuration
Annotations
@deprecated
Deprecated
use SizeRange instead
Exceptions thrown
IllegalArgumentException if specified value is less than zero.

Packages

Checkers

Companion object Checkers

trait Checkers extends Configuration

Property check configuration

Type Members

Value Members

Deprecated Value Members

Inherited from Configuration

Inherited from AnyRef

Inherited from Any

Ungrouped

Packages

Checkers 

Companion object Checkers

trait Checkers extends Configuration

Property check configuration

Type Members

Value Members

Deprecated Value Members

Inherited from Configuration

Inherited from AnyRef

Inherited from Any

Ungrouped

Checkers