JSVerify vs ScalaCheck

JSVerify is a free, open-source property-based testing library for JavaScript, inspired by QuickCheck. It generates inputs and checks whether a stated property holds across them. When a check fails, it attempts to shrink the generated input into a smaller counterexample. Properties can return Promises, allowing asynchronous methods to be tested. JSVerify is framework agnostic; the project names Mocha, nodeunit, and Jasmine as examples. The README instructs users to install it with `npm install jsverify` and says TypeScript typings are provided, though TypeScript specs cannot use the type DSL. Documented defaults are 100 tests and a maximum generated-value size of 50. Options cover test count, maximum generated size, quiet output, and random generator state. Generated values are deterministic when using primitives from the random module, and the RNG state can be set. The project is maintained by phadej and licensed under MIT. Its official site points to the GitHub README for API and usage documentation. The README cautions that exposed utility functions may change incompatibly, including in patch releases.

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.