Check a property.
Check a property.
the property to check
TestFailedException
if a test case is discovered for which the property doesn't hold.
Check a property with the given testing parameters.
Check a property with the given testing parameters.
the property to check
the test parameters
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 6-arg function into a property, and check it.
Convert the passed 6-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 5-arg function into a property, and check it.
Convert the passed 5-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 4-arg function into a property, and check it.
Convert the passed 4-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 3-arg function into a property, and check it.
Convert the passed 3-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 2-arg function into a property, and check it.
Convert the passed 2-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
Convert the passed 1-arg function into a property, and check it.
Convert the passed 1-arg function into a property, and check it.
the function to be converted into a property and checked
TestFailedException
if a test case is discovered for which the property doesn't hold.
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
:The
check
method, defined inCheckers
, makes it easy to write property-based tests inside ScalaTest, JUnit, and TestNG test suites. This example specifies a property thatList
'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 nameda
andb
. Inside the body of the function, you see: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 fora
andb
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 aTestFailedException
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'sRunner
, 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 supertraitConfiguration
. The five configuration parameters for property checks along with their default values and meanings are described in the following table:The
check
methods of traitCheckers
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 theCheckers
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
PropertyCheckConfiguration
object as an implicit parameter, thecheck
methods of traitCheckers
also take a variable length argument list ofPropertyCheckConfigParam
objects that you can use to override the values provided by the implicitPropertyCheckConfiguration
for a singlecheck
invocation. You place these configuration settings after the property or property function, For example, if you want to setminSuccessful
to 500 for just one particularcheck
invocation, you can do so like this:This invocation of
check
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:The previous configuration approach works the same in
Checkers
as it does inGeneratorDrivenPropertyChecks
. TraitCheckers
also provides onecheck
method that takes anorg.scalacheck.Test.Parameters
object, in case you want to configure ScalaCheck that way.For more information, see the documentation for supertrait
Configuration
.