JSVerify vs Racket QuickCheck

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.

Racket QuickCheck is a free package for checking program properties with generated inputs. A property is written as ordinary Racket code, and the package runs it against generated values; if a check fails, it reports a counterexample and the arguments that produced it. Its default configuration runs 100 successful tests, and helpers allow counts of 1,000, 10,000, or a custom number. Built-in generators cover integers, real numbers, characters, lists, vectors, strings, and symbols, and custom generators are supported. The `rackunit/quickcheck` integration raises a RackUnit exception when a check fails and includes the test count and counterexample arguments. Install the package with `raco pkg install quickcheck` or through DrRacket’s GUI package manager. It requires Racket v6.0 or newer. Racket provides installers for Linux, macOS, and Windows. The package listing reports a successful build and passing tests, while also noting missing license metadata. The listed price is free.