PropEr vs QCheck

PropEr is a free, open-source testing tool for Erlang programs. It performs automated, semi-random property-based testing and can generate input data from Erlang type declarations. Functions can be tested automatically from information in their Erlang specifications, while properties are written as Erlang expressions with predefined macros. PropEr also supports model-based random testing for stateful systems and targeted property-based testing using search-based techniques. Failing cases can be shrunk, and the project supports EUnit and Common Test. Constraints that Erlang’s type language cannot express can be handled with custom generators; filtering may keep trying random values until one passes. The generator language differs from Erlang’s type language for list expressions, including support for particular list lengths and element types. PropEr is self-hosted, supports Erlang, and is distributed under GPL version 3 or later. The guide describes installation from GitHub source, with make, or through Homebrew.

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.