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 thePropertyGenConfig
object passed implicitly to its apply
methods with parameter values passed to its constructor.
A PropertyCheckConfigParam
that specifies the maximum number of discarded
property evaluations allowed during property evaluation.
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 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 number of successful
property evaluations required for the property to pass.
Configuration object for property checks.
Abstract class defining a family of configuration parameters for property checks.
A PropertyCheckConfigParam
that specifies the number of worker threads
to use when evaluating a property.
o != arg0
is the same as !(o == (arg0))
.
o != arg0
is the same as !(o == (arg0))
.
the object to compare against this object for dis-equality.
false
if the receiver object is equivalent to the argument; true
otherwise.
o == arg0
is the same as if (o eq null) arg0 eq null else o.equals(arg0)
.
o == arg0
is the same as if (o eq null) arg0 eq null else o.equals(arg0)
.
the object to compare against this object for equality.
true
if the receiver object is equivalent to the argument; false
otherwise.
o == arg0
is the same as o.equals(arg0)
.
o == arg0
is the same as o.equals(arg0)
.
the object to compare against this object for equality.
true
if the receiver object is equivalent to the argument; false
otherwise.
This method is used to cast the receiver object to be of type T0
.
This method is used to cast the receiver object to be of type T0
.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression1.asInstanceOf[String]
will throw a ClassCastException
at runtime, while the expressionList(1).asInstanceOf[List[String]]
will not. In the latter example, because the type argument is erased as
part of compilation it is not possible to check whether the contents of the list are of the requested typed.
the receiver object.
This method creates and returns a copy of the receiver object.
This method creates and returns a copy of the receiver object.
The default implementation of the clone
method is platform dependent.
a copy of the receiver object.
This method is used to test whether the argument (arg0
) is a reference to the
receiver object (this
).
This method is used to test whether the argument (arg0
) is a reference to the
receiver object (this
).
The eq
method implements an [http://en.wikipedia.org/wiki/Equivalence_relation equivalence relation] on
non-null instances of AnyRef
:
* It is reflexive: for any non-null instance x
of type AnyRef
, x.eq(x)
returns true
.
* It is symmetric: for any non-null instances x
and y
of type AnyRef
, x.eq(y)
returns true
if and
only if y.eq(x)
returns true
.
* It is transitive: for any non-null instances x
, y
, and z
of type AnyRef
if x.eq(y)
returns true
and y.eq(z)
returns true
, then x.eq(z)
returns true
.
Additionally, the eq
method has three other properties.
* It is consistent: for any non-null instances x
and y
of type AnyRef
, multiple invocations of
x.eq(y)
consistently returns true
or consistently returns false
.
* For any non-null instance x
of type AnyRef
, x.eq(null)
and null.eq(x)
returns false
.
* null.eq(null)
returns true
.
When overriding the equals
or hashCode
methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2
), they
should be equal to each other (o1 == o2
) and they should hash to the same value (o1.hashCode == o2.hashCode
).
the object to compare against this object for reference equality.
true
if the argument is a reference to the receiver object; false
otherwise.
This method is used to compare the receiver object (this
) with the argument object (arg0
) for equivalence.
This method is used to compare the receiver object (this
) with the argument object (arg0
) for equivalence.
The default implementations of this method is an [http://en.wikipedia.org/wiki/Equivalence_relation equivalence
relation]:
* It is reflexive: for any instance x
of type Any
, x.equals(x)
should return true
.
* It is symmetric: for any instances x
and y
of type Any
, x.equals(y)
should return true
if and
only if y.equals(x)
returns true
.
* It is transitive: for any instances x
, y
, and z
of type AnyRef
if x.equals(y)
returns true
and
y.equals(z)
returns true
, then x.equals(z)
should return true
.
If you override this method, you should verify that your implementation remains an equivalence relation.
Additionally, when overriding this method it is often necessary to override hashCode
to ensure that objects
that are "equal" (o1.equals(o2)
returns true
) hash to the same
scala.Int
(o1.hashCode.equals(o2.hashCode)
).
the object to compare against this object for equality.
true
if the receiver object is equivalent to the argument; false
otherwise.
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.
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.
The details of when and if the finalize
method are invoked, as well as the interaction between finalize
and non-local returns and exceptions, are all platform dependent.
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 passedPropertyGenConfig
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 passedPropertyGenConfig
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 PropertyCheckConfig
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 representation that corresponds to the dynamic class of the receiver object.
Returns a representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
Returns a hash code value for the object.
Returns a hash code value for the object.
The default hashing algorithm is platform dependent.
Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)
) yet
not be equal (o1.equals(o2)
returns false
). A degenerate implementation could always return 0
.
However, it is required that if two objects are equal (o1.equals(o2)
returns true
) that they have
identical hash codes (o1.hashCode.equals(o2.hashCode)
). Therefore, when overriding this method, be sure
to verify that the behavior is consistent with the equals
method.
the hash code value for the object.
This method is used to test whether the dynamic type of the receiver object is T0
.
This method is used to test whether the dynamic type of the receiver object is T0
.
Note that the test result of the test is modulo Scala's erasure semantics. Therefore the expression1.isInstanceOf[String]
will return false
, while the expression List(1).isInstanceOf[List[String]]
will
return true
. In the latter example, because the type argument is erased as part of compilation it is not
possible to check whether the contents of the list are of the requested typed.
true
if the receiver object is an instance of erasure of type T0
; false
otherwise.
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.
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.
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.
o.ne(arg0)
is the same as !(o.eq(arg0))
.
o.ne(arg0)
is the same as !(o.eq(arg0))
.
the object to compare against this object for reference dis-equality.
false
if the argument is not a reference to the receiver object; true
otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
a string representation of the object.
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.ShouldMatchers._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 be === 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.
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
(andShouldMatchers
) 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: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 are 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 aPropertyCheckConfig
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, if 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
PropertyCheckConfig
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 implicitPropertyCheckConfig
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 passedPropertyCheckConfig
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
.