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.
This version of Checkers was tested with ScalaCheck version 1.1.1. This trait must
be mixed into a ScalaTest Suite, because its self type is org.scalatest.Suite.
Check a property.
Check a property.
the property to check
Check a property with the given testing parameters.
Check a property with the given testing parameters.
the property to check
the test parameters
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
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
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
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
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
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
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
checkmethod, 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 namedaandb. Inside the body of the function, you see:The property in this case is a
Booleanexpression 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 foraandband 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,checkreturns normally. Otherwise,checkwill complete abruptly with aTestFailedExceptionthat 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
Checkerswith ScalaTest'sRunner, you must include ScalaCheck's jar file on the class path or runpath. This version ofCheckerswas tested with ScalaCheck version 1.1.1. This trait must be mixed into a ScalaTestSuite, because its self type isorg.scalatest.Suite.