test basics in haskell

hsp.hs

module Main where

import Test.Hspec
import Test.QuickCheck

sqr :: Integer -> Integer
sqr n = n * n

squareNumberIsGreaterOrEqualToZero :: Integer -> Bool
squareNumberIsGreaterOrEqualToZero n = sqr n >= 0

theOtherProperty :: Integer -> Bool
theOtherProperty n = let bign = (abs n) + 1
                     in sqr bign >= bign

theThird :: Integer -> Bool
theThird n = (round $ sqrt (fromIntegral $ sqr n)) == abs n

main :: IO ()
main = do
  quickCheck squareNumberIsGreaterOrEqualToZero
  quickCheck theOtherProperty
  quickCheck theThird
  hspec $ describe "square function" $ do
    it "the square of 0 is 0" $
      sqr 0 `shouldBe` 0

    it "the square of 1 is 1" $
      sqr 1 `shouldBe` 1

    it "the square of 2 is 4" $
      sqr 2 `shouldBe` 4