[Haskell-beginners] QuickCheck with monadic IO

[Hartmut]

Everyone,

I want to run an QuickCheck on "a most simple" IO monad.
When I compile and run :main, it says:
....................................................................................................+++
OK, passed 100 tests.
Well, thats fine, since *1 mapped on any Int gives the same Int back.
But it lasts 10 seconds (!) for doing those 100 Tests.
Something must be wrong?!
I'd appreciate your ideas.

Hartmut


module MonadicQuickCheck where

import IO
import Random
import Test.QuickCheck
import Test.QuickCheck.Monadic

main = do
  quickCheck x

x :: Property
x = monadicIO $ do
  a <- pick arbitrary
  pre $ not(null a)
  b <- run $ testfunction a
  assert $ b == a

testfunction :: [Int] -> IO [Int]
testfunction x = do
  putStr "."
  return $ map (*1) x
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