[Haskell-cafe] ANN: leancheck-v0.7.2, enumerative QuickCheck-like testing

Rudy Matela rudy at matela.com.br
Wed Aug 22 22:06:03 UTC 2018

Hello Haskell-Café,

LeanCheck is a simple enumerative property-based testing library for
Haskell.  It is highly portable, and even works on Hugs98 (v2006-09).
It does not pull any dependencies other than what's bundled with GHC.
Check it out on Hackage and GitHub:


A simple example follows:

	> import Test.LeanCheck
	> import Data.List (sort, union)

	> check $ \xs -> sort (sort xs) == sort (xs::[Int])
	+++ OK, passed 200 tests.

	> check $ \xs ys -> xs `union` ys == ys `union` (xs::[Int])
	*** Failed! Falsifiable (after 4 tests):
	[] [0,0]

LeanCheck works on all types that are instances of the Listable typeclass.
A TH automatic deriver is provided with LeanCheck so you don't need to
learn LeanCheck's DSL to test with your types.

I recently released 0.7.2, there are several additions since last
announcement here.  Notable changes include:

* minor fixes for loading on Hugs98;
* functions to compute statistics about generated values; and
* a family of functions to test invariants of typeclass instances:

	> data MyTy = ...
	> instance ... MyTy where ...
	> import Test.LeanCheck.Utils
	> check $ (okEqOrd :: MyTy -> MyTy -> MyTy -> Bool)
	+++ OK, passed 200 tests.
	> check $ (okNum   :: MyTy -> MyTy -> MyTy -> Bool)
	+++ OK, passed 200 tests.

LeanCheck is available on Hackage or Stackage, and can be installed using:

	$ cabal install leancheck

As far as I am aware, there are no bindings to use LeanCheck with tasty,
test-framework or hspec yet, but contributions are welcome.  I may create
bindings for those if I ever get the time.

Best Regards,

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