Performs a configured property checks by applying property check functions passed to its apply
methods to arguments
supplied by implicitly passed generators, modifying the values in the
PropertyGenConfig
object passed implicitly to its apply
methods with parameter values passed to its constructor.
Performs a configured property checks by applying property check functions passed to its apply
methods to arguments
supplied by implicitly passed generators, modifying the values in the
PropertyGenConfig
object passed implicitly to its apply
methods with parameter values passed to its constructor.
Instances of this class are returned by trait GeneratorDrivenPropertyChecks
forAll
method that accepts a variable length
argument list of PropertyCheckConfigParam
objects. Thus it is used with functions of all six arities.
Here are some examples:
forAll (minSize(1), maxSize(10)) { (a: String) => a.length should equal ((a).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String) => a.length + b.length should equal ((a + b).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
In the first example above, the ConfiguredPropertyCheck
object is returned by:
forAll (minSize(1), maxSize(10))
The code that follows is an invocation of one of the ConfiguredPropertyCheck
apply
methods:
{ (a: String) =>
a.length should equal ((a).length)
}
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).
IllegalArgumentException
if specified value
is less than zero.
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.
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).
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.
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.
IllegalArgumentException
if specified value
is less than or equal to zero.
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.
IllegalArgumentException
if specified value
is less than zero.
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.
use SizeRange instead
IllegalArgumentException
if specified value
is less than zero.
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 |
the minimum number of successful property evaluations required for the property to pass.
the maximum number of discarded property evaluations allowed during a property check
the minimum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
the maximum size parameter to provide to ScalaCheck, which it will use when generating objects for which size matters (such as strings or lists).
specifies the number of worker threads to use during property evaluation
Use PropertyCheckConfiguration instead
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.
Use PropertyCheckConfiguration directly instead.
Implicitly converts PropertyCheckConfig
s to PropertyCheckConfiguration
,
which enables a smoother upgrade path.
Implicitly converts PropertyCheckConfig
s to PropertyCheckConfiguration
,
which enables a smoother upgrade path.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a"), (famousLastWords, "b"), (famousLastWords, "c"), (famousLastWords, "d"), (famousLastWords, "e"), (famousLastWords, "f")) { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords, famousLastWords, famousLastWords, famousLastWords, famousLastWords, famousLastWords) { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a", "b", "c", "d", "e", "f") { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a"), (famousLastWords, "b"), (famousLastWords, "c"), (famousLastWords, "d"), (famousLastWords, "e")) { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords, famousLastWords, famousLastWords, famousLastWords, famousLastWords) { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a", "b", "c", "d", "e") { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a"), (famousLastWords, "b"), (famousLastWords, "c"), (famousLastWords, "d")) { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords, famousLastWords, famousLastWords, famousLastWords) { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a", "b", "c", "d") { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a"), (famousLastWords, "b"), (famousLastWords, "c")) { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords, famousLastWords, famousLastWords) { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a", "b", "c") { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a"), (famousLastWords, "b")) { (a: String, b: String) => a.length + b.length should equal ((a + b).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords, famousLastWords) { (a: String, b: String) => a.length + b.length should equal ((a + b).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a", "b") { (a: String, b: String) => a.length + b.length should equal ((a + b).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String, b: String) => a.length + b.length should equal ((a + b).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to named arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll ((famousLastWords, "a")) { (a: String) => a.length should equal ((a).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Performs a property check by applying the specified property check function to arguments supplied by the specified generators.
Here's an example:
import org.scalacheck.Gen // Define your own string generator: val famousLastWords = for { s <- Gen.oneOf("the", "program", "compiles", "therefore", "it", "should", "work") } yield s forAll (famousLastWords) { (a: String) => a.length should equal ((a).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function with the specified argument names to arguments supplied by implicitly passed generators.
Here's an example:
forAll ("a") { (a: String) => a.length should equal ((a).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Performs a property check by applying the specified property check function to arguments supplied by implicitly passed generators.
Here's an example:
forAll { (a: String) => a.length should equal ((a).length) }
the property check function to apply to the generated arguments
Performs a property check by applying the specified property check function to arguments
supplied by implicitly passed generators, modifying the values in the implicitly passed
PropertyGenConfig
object with explicitly passed parameter values.
Performs a property check by applying the specified property check function to arguments
supplied by implicitly passed generators, modifying the values in the implicitly passed
PropertyGenConfig
object with explicitly passed parameter values.
This method creates a ConfiguredPropertyCheck
object that has six overloaded apply methods
that take a function. Thus it is used with functions of all six arities.
Here are some examples:
forAll (minSize(1), maxSize(10)) { (a: String) => a.length should equal ((a).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String) => a.length + b.length should equal ((a + b).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String) => a.length + b.length + c.length should equal ((a + b + c).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String) => a.length + b.length + c.length + d.length should equal ((a + b + c + d).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String, e: String) => a.length + b.length + c.length + d.length + e.length should equal ((a + b + c + d + e).length) } forAll (minSize(1), maxSize(10)) { (a: String, b: String, c: String, d: String, e: String, f: String) => a.length + b.length + c.length + d.length + e.length + f.length should equal ((a + b + c + d + e + f).length) }
a variable length list of PropertyCheckConfigParam
objects that should override corresponding
values in the PropertyCheckConfiguration
implicitly passed to the apply
methods of the ConfiguredPropertyCheck
object returned by this method.
Implicit PropertyCheckConfig
value providing default configuration values.
Implicit PropertyCheckConfig
value providing default configuration values.
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.
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).
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.
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.
Evaluates the passed code block if the passed boolean condition is true, else throws DiscardedEvaluationException
.
Evaluates the passed code block if the passed boolean condition is true, else throws DiscardedEvaluationException
.
The whenever
method can be used inside property check functions to discard invocations of the function with
data for which it is known the property would fail. For example, given the following Fraction
class:
class Fraction(n: Int, d: Int) { require(d != 0) require(d != Integer.MIN_VALUE) require(n != Integer.MIN_VALUE) val numer = if (d < 0) -1 * n else n val denom = d.abs override def toString = numer + " / " + denom }
import org.scalatest.prop.TableDrivenPropertyChecks._ val fractions = Table( ("n", "d"), ( 1, 2), ( -1, 2), ( 1, -2), ( -1, -2), ( 3, 1), ( -3, 1), ( -3, 0), ( 3, -1), ( 3, Integer.MIN_VALUE), (Integer.MIN_VALUE, 3), ( -3, -1) )
Imagine you wanted to check a property against this class with data that includes some
value that are rejected by the constructor, such as a denominator of zero, which should
result in an IllegalArgumentException
. You could use whenever
to discard any rows in the fraction
that represent illegal arguments, like this:
import org.scalatest.matchers.Matchers._ forAll (fractions) { (n: Int, d: Int) => whenever (d != 0 && d != Integer.MIN_VALUE && n != Integer.MIN_VALUE) { val f = new Fraction(n, d) if (n < 0 && d < 0 || n > 0 && d > 0) f.numer should be > 0 else if (n != 0) f.numer should be < 0 else f.numer should === (0) f.denom should be > 0 } }
In this example, rows 6, 8, and 9 have values that would cause a false to be passed
to whenever
. (For example, in row 6, d
is 0, which means d
!=
0
will be false.) For those rows, whenever
will throw DiscardedEvaluationException
,
which will cause the forAll
method to discard that row.
the boolean condition that determines whether whenever
will evaluate the
fun
function (condition
is true) or throws DiscardedEvaluationException
(condition
is false)
the function to evaluate if the specified condition
is true
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.
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.
use maxDiscardedFactor instead
IllegalArgumentException
if specified value
is less than zero.
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.
use SizeRange instead
IllegalArgumentException
if specified value
is less than zero.
Trait containing methods that faciliate property checks against generated data using ScalaCheck.
This trait contains
forAll
methods that provide various ways to check properties using generated data. Use of this trait requires that ScalaCheck be on the class path when you compile and run your tests. It also contains awherever
method that can be used to indicate a property need only hold whenever some condition is true.For an example of trait
GeneratorDrivenPropertyChecks
in action, imagine you want to test thisFraction
class:To test the behavior of
Fraction
, you could mix in or import the members ofGeneratorDrivenPropertyChecks
(andMatchers
) and check a property using aforAll
method, like this:Trait
GeneratorDrivenPropertyChecks
provides overloadedforAll
methods that allow you to check properties using the data provided by a ScalaCheck generator. The simplest form offorAll
method takes two parameter lists, the second of which is implicit. The first parameter list is a "property" function with one to six parameters. An implicitArbitrary
generator andShrink
object needs to be supplied for TheforAll
method will pass each row of data to each parameter type. ScalaCheck provides many implicitArbitrary
generators for common types such asInt
,String
,List[Float]
, etc., in itsorg.scalacheck.Arbitrary
companion object. So long as you use types for which ScalaCheck already provides implicitArbitrary
generators, you needn't worry about them. Same forShrink
objects, which are provided by ScalaCheck'sorg.scalacheck.Shrink
companion object. Most often you can simply pass a property function toforAll
, and the compiler will grab the implicit values provided by ScalaCheck.The
forAll
methods use the suppliedArbitrary
generators to generate example arguments and pass them to the property function, and generate aGeneratorDrivenPropertyCheckFailedException
if the function completes abruptly for any exception that would normally cause a test to fail in ScalaTest other thanDiscardedEvaluationException
. AnDiscardedEvaluationException
, which is thrown by thewhenever
method (defined in traitWhenever
, which this trait extends) to indicate a condition required by the property function is not met by a row of passed data, will simply causeforAll
to discard that row of data.Supplying argument names
You can optionally specify string names for the arguments passed to a property function, which will be used in any error message when describing the argument values that caused the failure. To supply the names, place them in a comma separated list in parentheses after
forAll
before the property function (a curried form offorAll
). Here's an example:When this fails, you'll see an error message that includes this:
When you don't supply argument names, the error message will say
arg0
,arg1
, etc.. For example, this property check:Will fail with an error message that includes:
Supplying generators
ScalaCheck provides a nice library of compositors that makes it easy to create your own custom generators. If you want to supply custom generators to a property check, place them in parentheses after
forAll
, before the property check function (a curried form offorAll
).For example, to create a generator of even integers between (and including) -2000 and 2000, you could write this:
Given this generator, you could use it on a property check like this:
Custom generators are necessary when you want to pass data types not supported by ScalaCheck's arbitrary generators, but are also useful when some of the values in the full range for the passed types are not valid. For such values you would use a
whenever
clause. In theFraction
class shown above, neither the passed numerator or denominator can beInteger.MIN_VALUE
, and the passed denominator cannot be zero. This shows up in thewhenever
clause like this:whenever (d != 0 && d != Integer.MIN_VALUE && n != Integer.MIN_VALUE) { ...
You could in addition define generators for the numerator and denominator that only produce valid values, like this:
You could then use them in the property check like this:
Note that even if you use generators that don't produce the invalid values, you still need the
whenever
clause. The reason is that once a property fails, ScalaCheck will try and shrink the values to the smallest values that still cause the property to fail. During this shrinking process ScalaCheck may pass invalid values. Thewhenever
clause is still needed to guard against those values. (Thewhenever
clause also clarifies to readers of the code exactly what the property is in a succinct way, without requiring that they find and understand the generator definitions.)Supplying both generators and argument names
If you want to supply both generators and named arguments, you can do so by providing a list of
(<generator>, <name>)
pairs in parentheses afterforAll
, before the property function. Here's an example:Were this property check to fail, it would mention the names n and d in the error message, like this:
Property check configuration
The property checks performed by the
forAll
methods of this trait can be flexibly configured via the services provided by supertraitConfiguration
. The five configuration parameters for property checks along with their default values and meanings are described in the following table:The
forAll
methods of traitGeneratorDrivenPropertyChecks
each take aPropertyCheckConfiguration
object as an implicit parameter. This object provides values for each of the five configuration parameters. TraitConfiguration
provides an implicitval
namedgeneratorDrivenConfig
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 theGeneratorDrivenPropertyChecks
companion object rather than mixing in the trait.) For example, if you want all parameters at their defaults except forminSize
andmaxSize
, you can overridegeneratorDrivenConfig
, like this:Or, hide it by declaring a variable of the same name in whatever scope you want the changed values to be in effect:
In addition to taking a
PropertyCheckConfiguration
object as an implicit parameter, theforAll
methods of traitGeneratorDrivenPropertyChecks
also take a variable length argument list ofPropertyCheckConfigParam
objects that you can use to override the values provided by the implicitPropertyCheckConfiguration
for a singleforAll
invocation. For example, if you want to setminSuccessful
to 500 for just one particularforAll
invocation, you can do so like this:This invocation of
forAll
will use 500 forminSuccessful
and whatever values are specified by the implicitly passedPropertyCheckConfiguration
object for the other configuration parameters. If you want to set multiple configuration parameters in this way, just list them separated by commas:If you are using an overloaded form of
forAll
that already takes an initial parameter list, just add the configuration parameters after the list of generators, names, or generator/name pairs, as in:For more information, see the documentation for supertrait
Configuration
.