Shouldn't this be what you need?

testRnd.hs

import System.Random

-- Test validity of function on a given number of random tests.
testRandom :: Random a => StdGen -> Int -> (a -> Bool) -> Bool
testRandom gen n f = all f generated
  where generated = take n $ randoms gen

-- Examples of use in GHCi:
-- r <- getStdGen
-- testRandom r 100 ((\a -> a==a) :: Int -> Bool)