This is QuickCheck 2, a library for random testing of program properties. Add `QuickCheck` to your package dependencies to use it in tests or REPL. The quickcheck-instances [1] companion package provides instances for types in Haskell Platform packages at the cost of additional dependencies. The make-hugs script makes a Hugs-compatible version of QuickCheck. It may also be useful for other non-GHC implementations. [1]: http://hackage.haskell.org/package/quickcheck-instances