QuickCheck

It is compatible with the compiler, Glasgow Haskell Compiler (GHC) and the interpreter, Haskell User's Gofer System (Hugs).

It is free and open-source software released under a BSD-style license.

In QuickCheck, assertions are written about logical properties that a function should fulfill.

Then QuickCheck attempts to generate a test case that falsifies such assertions.

Once such a test case is found, QuickCheck tries to reduce it to a minimal failing subset by removing or simplifying input data that are unneeded to make the test fail.