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
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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 specifiedvalue
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 traitsPropertyChecks
(for ScalaTest-style property checks) andCheckers
(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 specifiedvalue
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 throwsDiscardedEvaluationException
, which is produce bywhenever
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 withDiscardedEvaluationException
.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 specifiedvalue
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 theforAll
methods of traitsPropertyChecks
andCheckers
. 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 specifiedvalue
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 specifiedminSuccessful
value is less than or equal to zero, the specifiedmaxDiscarded
value is less than zero, the specifiedminSize
value is less than zero, the specifiedmaxSize
value is less than zero, the specifiedminSize
is greater than the specified or default value ofmaxSize
, or the specifiedworkers
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
PropertyCheckConfig
s toPropertyCheckConfiguration
, which enables a smoother upgrade path.Implicitly converts
PropertyCheckConfig
s toPropertyCheckConfiguration
, 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
- @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
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
-
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
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
-
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
- @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 specifiedvalue
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 theforAll
methods of traitsPropertyChecks
andCheckers
. 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 specifiedvalue
is less than zero.