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--------------------------------------------------------------------------
-- Some tests from Sebastian's tutorial on EasyCheck.
-- In order to write a test, we have to import the module Test.Prop:
import Test.Prop
--------------------------------------------------------------------------
-- Deterministic tests:
appendIsAssociative xs ys zs = (xs ++ ys) ++ zs -=- xs ++ (ys ++ zs)
reverseLeavesSingletonUntouched x = reverse [x] -=- [x]
reverseOfNonemptyIsNotNull x xs = reverse (x:xs) `is` (not . null)
reverseAntiDistributesOverAppend xs ys
= reverse (xs++ys) -=- reverse ys ++ reverse xs
-- Testing non-deterministic operations:
insert :: a -> [a] -> [a]
insert x xs = x : xs
insert x (y:ys) = y : insert x ys
insertIsNeverNull :: Int -> [Int] -> Prop
insertIsNeverNull x xs = insert x xs `isAlways` (not . null)
insertInsertsAsHead :: Int -> [Int] -> Prop
insertInsertsAsHead x xs = insert x xs ~> x:xs
--------------------------------------------------------------------------
|
