fast-check vs ScalaCheck

fast-check is a property-based testing library for JavaScript and TypeScript. It generates inputs and checks expected behavior across many cases, then reduces a failure to a smaller counterexample to help investigate it. Tests combine arbitraries that create values, properties that describe behavior, runners that execute checks, and plugins that extend runners. It works with Jest, Mocha, Vitest, Ava, Bun, Deno, the Node.js test runner, and other test runners. Runs can be configured with seeds, generated-value sizes, time limits, and result reporting globally or per assertion. fast-check supports stateful testing and reproducible failures; its project also describes fuzzing and generative testing for issues such as race conditions and prototype poisoning. The project is open source under the MIT license, and the listed plan is free. Version 5.x requires Node.js 22.12.0 or later and ECMAScript 2025; TypeScript 5.8 or later is optional.

ScalaCheck is a free Scala library for automated property-based testing of Scala and Java programs. It checks defined properties against randomized input parameters and reports the arguments that produce a failure. The library supports parameterized cases and parallel execution, and can run on its own with a built-in test runner. For sbt projects, the site shows how to add it as a test dependency; it is also integrated with ScalaTest, specs2 and LambdaTest. ScalaCheck has no external dependencies beyond the Scala runtime. Build artifacts are published in the Central Repository, with an sbt dependency declaration available from the download page. Documentation includes a user guide and API reference. The site lists version 1.19.0, released September 6, 2025. The project identifies the BSD-3-Clause license and lists a security policy. Its build defines JVM, Scala.js and Scala Native platforms, and its README says the Gradle plugin supports Scala.js and Scala Native. The site names the Scala compiler and Akka among projects that use it.