ScalaCheck

ScalaCheck is a library written in the Scala Programming Language and is used for automated specification-based testing of Scala or Java software applications. ScalaCheck was originally inspired by the Haskell library QuickCheck, but has also ventured into its own.

ScalaCheck has no dependencies other than the Scala runtime, and is supported by SBT, ScalaTest and Specs2. You can of course also use ScalaCheck completely standalone, with its built-in test runner.

Quick start

Specify some of the methods of java.util.String like this:

import org.scalacheck.Properties
import org.scalacheck.Prop.forAll

object StringSpecification extends Properties("String") {
  property("startsWith") = forAll((a: String, b: String) => (a+b).startsWith(a))

  property("concatenate") = forAll((a: String, b: String) =>
    (a+b).length > a.length && (a+b).length > b.length
  )

  property("substring") = forAll((a: String, b: String, c: String) =>
    (a+b+c).substring(a.length, a.length+b.length) == b
  )
}

Then compile and run the tests like this:

$ scalac -cp scalacheck.jar StringSpecification.scala

$ scala -cp .:scalacheck.jar StringSpecification
+ String.startsWith: OK, passed 100 tests.
! String.concat: Falsified after 0 passed tests.
> ARG_0: ""
> ARG_1: ""
+ String.substring: OK, passed 100 tests.

As we can see, the second property was not quite right. ScalaCheck discovers this and presents the arguments that make the property fail, two empty strings. The other two properties both pass 100 test rounds, each with a randomized set of input parameters.

Documentation

Download

The current release of ScalaCheck is 1.9, and it is available in the Sonatype OSS repository. There should be builds available for all 2.9.x versions of Scala. If you lack some build, please submit an issue. ScalaCheck 1.9 is unfortunately not compatible with Scala 2.8.x. If you need to use ScalaCheck with an old version of Scala, please check out the previous releases.

Notice, ScalaCheck was previously published under the repository group id (or organization) org.scala-tools.testing, but this has been changed to org.scalacheck. Please make sure to update your dependencies. The current ScalaCheck release might still be available under the old id, but new builds will only be published under the new id.

If you are using SBT, add the following to your build file to make ScalaCheck available in your project:

resolvers ++= Seq(
  "snapshots" at "http://oss.sonatype.org/content/repositories/snapshots",
  "releases"  at "http://oss.sonatype.org/content/repositories/releases"
)

libraryDependencies ++= Seq(
  "org.scalacheck" %% "scalacheck" % "1.9" % "test"
)

If you are using Maven, the following will do the trick:

<dependency>
  <groupId>org.scalacheck</groupId>
  <artifactId>scalacheck_2.9.1</artifactId>
  <version>1.9</version>
  <scope>test</scope>
</dependency>

<repository>
  <id>oss.sonatype.org</id>
  <name>releases</name>
  <url>http://oss.sonatype.org/content/repositories/releases</url>
</repository>

<repository>
  <id>oss.sonatype.org</id>
  <name>snapshots</name>
  <url>http://oss.sonatype.org/content/repositories/snapshots</url>
</repository>

<repository>
  <id>central</id>
  <name>Maven repository</name>
  <url>http://repo1.maven.org/maven2</url>
</repository>

<repository>
  <id>ObjectWeb</id>
  <name>ObjectWeb repository</name>
  <url>http://maven.ow2.org/maven2</url>
</repository>

Bugs and feature requests

Please feel free to submit any bugs you find or feature requests you have in the issue tracker here at GitHub. Pull requests are of course also welcome!

Build instructions

ScalaCheck uses SBT for building, and the root directory contains an SBT launcher which makes building very easy. Just clone the git repository and build ScalaCheck in the following way:

./sbt update
./sbt compile

Run the test suite like this:

./sbt test

The tests for ScalaCheck is of course written in ScalaCheck. SBT even handles bootstrapping, so the newly built ScalaCheck will be used to run the tests on itself.

novus / scalacheck