@hackage hstest0.0.0

hstest looks through all Haskell source files in the current directory (by default), finds all properties to test (properties must have a name that starts prop_), and runs them via QuickCheck.

For example, suppose you have this Haskell source file called mysort.hs:

mySort xs = ... -- a function you wish to test (definition elided)

prop_lengthStaysTheSame xs = length xs == length (mySort xs)
prop_sumStaysTheSame xs = sum xs == sum (mySort xs)
prop_lowestElementAtStart, prop_highestElementAtEnd :: [Int] -> Bool
prop_lowestElementAtStart xs = not (null xs) ==> minimum xs = head (mySort xs)
prop_highestElementAtEnd xs = not (null xs) ==> maximum xs = last (mySort xs)

Then to check all these tests, you run

$ hstest
Failed prop_highestElementAtEnd:
 *  [-3,2,-2]
mysort.hs: Failed 1 property, passed 3 properties

Oops! Fix mySort and try again:

$ hstest
mysort.hs: Passed 4 properties