sort . sort = sort
+++ Tests passed.

length . nub = length  (incorrect when there are repeated elements)
*** Falsified, counterexample:  [0,0] :: [Int]
               generalization:  x:x:xs :: [Int]

\(x,y) -> x + y == y + x
+++ Tests passed.

\x -> x == x + 1  (always incorrect)
*** Falsified, counterexample:  0 :: Int
               generalization:  x :: Int

\(x,y) -> x + y == x + x  (incorrect)
*** Falsified, counterexample:  (0,1) :: (Int,Int)

\(x,y) -> x /= y  (incorrect whenever x and y are equal)
*** Falsified, counterexample:  (0,0) :: (Int,Int)
               generalization:  (x,x) :: (Int,Int)