QuickCheck

For checking properties.

Usage

module MyModule where
import Test.QuickCheck

prop_absolute :: Int -> Int -> Bool
prop_absolute a b = (absolute a) * (absolute b) == absolute (a * b)

> quickCheck prop_absolute
+++ OK, passed 100 tests.

Testing Certain Values

• Implication function: premise ==> conclusion

prop_absolute :: Int -> Int -> Property
prop_absolute a b = let a' = toInteger a
                        b' = toInteger b
                        maxInt = toInteger (maxBound :: Int)
                        minInt = toInteger (minBound :: Int)
                    in
                        (a' * b' < maxInt && a' * b' > minInt)
                        ==> (absolute a) * (absolute b) == absolute (a * b)

-- equals
prop_absolute' :: Int -> Int -> Property
prop_absolute' a b = (a' * b' < maxInt && a' * b' > minInt)
                        ==> (absolute a) * (absolute b) == absolute (a * b)
                    where
                        a' = toInteger a
                        b' = toInteger b
                        maxInt = toInteger (maxBound :: Int)
                        minInt = toInteger (minBound :: Int)