ScalaCheck

ScalaCheck is a free library for automated property-based testing of Scala and Java programs. It is best suited to teams already working in Scala build and test workflows. Its focused approach can expose failing inputs across randomized cases without adding a separate paid plan.

Overview

Instead of checking only hand-picked examples, ScalaCheck evaluates properties over randomized inputs and reports the arguments that make a property fail. This is useful when a rule should hold across many possible values: the reported case gives developers something specific to investigate. It does not determine which behaviors matter, so teams still need to define meaningful properties.

ScalaCheck's only external dependency is the Scala runtime. That keeps its dependency footprint narrow, but makes it a poor fit for projects that cannot accommodate that runtime. The project is licensed under BSD-3-Clause.

Key features

Randomized property checks

Parameterized cases and property-based checks let developers examine behavior across varied inputs, while reported failing arguments make a broken property more actionable. Parallel execution is supported, which can suit suites that want to run checks concurrently; the value still depends on writing useful properties in the first place.

Build and framework integration

ScalaCheck works with sbt and integrates with ScalaTest, specs2, and LambdaTest. Teams already using those tools can incorporate property checks into familiar workflows rather than relying only on standalone execution. It can also run with its built-in test runner, providing an option when framework integration is not needed.

Build artifacts are published in the Central Repository, and the project recommends adding version 1.19.0 as an sbt test dependency. Its build defines JVM, Scala.js, and Scala Native targets; the README also notes support from the Gradle plugin for Scala.js and Scala Native.

Pricing

ScalaCheck's free plan costs nothing and provides the open-source library under a BSD-3-Clause license. There is no free trial, because there is no paid tier to trial. No seat or usage quota is attached to the plan. This makes it straightforward to consider for teams that need property checks without a software fee, though adopting it still requires the Scala runtime.

Platforms

ScalaCheck supports Linux, macOS, and Windows. Its build targets JVM, Scala.js, and Scala Native, giving Scala projects more than a JVM-only target choice. Documentation includes a continuously developed user guide and latest-release API documentation. Support routes include GitHub bug reports, a mailing list, and Stack Overflow; the repository also lists a security policy.

Who it's for

ScalaCheck is a sensible choice for Scala and Java developers who want randomized checks for program properties and already use sbt or one of its integrated test frameworks. It is particularly relevant when a behavior can be expressed as a rule over many inputs, rather than a handful of fixed examples. Developers seeking a broad testing framework, or projects unable to use the Scala runtime, should look elsewhere.

Pros and cons

• Actionable failing cases: ScalaCheck reports the arguments that falsify a property, helping developers investigate a specific failure.
• Several integration paths: sbt, ScalaTest, specs2, and LambdaTest support make it easier to fit property checks into existing Scala workflows.
• Free and BSD-3-Clause licensed: There is no software charge for the library, and its license is identified as BSD-3-Clause.
• Runtime dependency: The Scala runtime is required, limiting its appeal for projects that need a runtime-independent testing library.
• Focused scope: It checks properties but does not replace the work of defining expected behavior or the need for other testing approaches.

Alternatives

For a language-specific alternative, Racket QuickCheck is free and requires Racket v6.0 or newer, so it is the more relevant choice for Racket projects. FsCheck is a free BSD-licensed library distributed through NuGet packages, making it an option for developers seeking that package ecosystem instead of ScalaCheck's Scala workflow.

fast-check is a free, MIT-licensed JavaScript/TypeScript option for web or API environments. Go developers can consider Gopter, a free MIT-licensed Go property-testing library. JSVerify is a free open-source JavaScript property-based testing library, while PropCheck is a free MIT-licensed Ruby gem requiring Ruby 2.5.1 or newer. QCheck is a free OCaml property-testing library under BSD-2-Clause. For another Scala testing library, Scala Hedgehog is free and has no paid plans.

Browse Property-Based Testing Tools or Unit Testing Frameworks to compare more options.

Verdict

Choose ScalaCheck if you work in Scala or Java and want a free way to check properties against randomized inputs, especially if sbt or one of its integrated frameworks is already part of your workflow. Its ability to report failing arguments is the clearest reason to choose it. Look elsewhere if you cannot use the Scala runtime or need a general-purpose testing framework rather than a focused property-checking library.