Gopter vs QCheck

Gopter is a free Go module for property-based testing. It creates properties from conditions and generated inputs, then checks whether those properties hold. Its generators provide more control than Go's testing/quick package and can be composed with operations such as Map, FlatMap, SuchThat, and WithShrinker. When a property fails, shrinkers seek a smaller value that still demonstrates the failure. Gopter also includes a generator for regular-expression matches and supports stateful tests based on arbitrary commands. Properties can run with Go's testing.T through TestingRun, and the gopter/convey package provides helpers for using Gopter inside GoConvey tests. Console and formatted reporters present test results. The project declares Go 1.20 and is distributed under the MIT License. Its documentation covers the gopter, gen, prop, arbitrary, commands, and convey packages. The README identifies two omissions: ScalaCheck's Pretty feature is not provided, and parallel commands are not available yet.

QCheck is a property-based testing library for OCaml, inspired by QuickCheck. Rather than relying only on hand-picked examples, it provides combinators to generate values such as lists, arrays, tuples, recursive types, and algebraic types for checking properties. When a check fails, generators can be paired with printers and shrinkers to show and reduce counterexamples. QCheck2 builds shrinking into its generators, though the project describes that API as less battle-tested than QCheck. The package family includes qcheck-core, qcheck-ounit, qcheck-alcotest, qcheck, and ppx_deriving_qcheck; the last can derive generators from type declarations. Runner options include QCheck_base_runner in qcheck-core and QCheck_runner with OUnit compatibility in qcheck, with integration layers for OUnit and Alcotest. The project also points to qcheck-stm for sequential and parallel model-based tests and qcheck-lin for sequential consistency testing. Installation is available through opam, and the source can be built with make. The minimal qcheck-core package depends only on unix and dune. QCheck is free and licensed under BSD-2-Clause.