StrictCheck is a property-based random testing framework for observing, specifying, and testing the strictness behaviors of Haskell functions. Strictness behavior is traditionally considered a non-functional property; StrictCheck allows it to be tested as if it were one, by reifying demands on data structures so they can be manipulated and examined within Haskell.
For details, see the library on Hackage: https://hackage.haskell.org/package/StrictCheck.