Testing my own sort function by comparing it to the standard library sort for many random test cases.

MySortExample.hs

import Data.List
import Test.QuickCheck

mySort :: [Int] -> [Int]
mySort list =
    let swapped = swap list in
    if swapped == list
        then list
        else mySort swapped
    where
        swap []         = []
        swap [x]        = [x]
        swap (a:b:xs)
            | a > b     = b:(swap (a:xs))
            | otherwise = a:(swap (b:xs))

genList :: Gen [Int]
genList = arbitrary

prop_mySortEqualToStdLibSort = forAllShrink genList shrink $ \xs ->
    mySort xs === sort xs

main = do
    sample genList
    quickCheck prop_mySortEqualToStdLibSort

Example output:

$ runhaskell MySortExample.hs
[]
[]
[4,1,2]
[-2,-3]
[3,6,-6,-2,4,6,-2]
[-4,-8,-6,-4,4,2,6,8]
[6,0,3]
[-2,-3,4,-13,11,9,9,-10,0,12,6,-14,8,10]
[]
[-10,-2,-13,1,-13,-14,-4,11,9,11,-18]
[1,-1,16,10,-2,-11]
+++ OK, passed 100 tests.