[Haskell-beginners] Cannot find cause of space leak

[YCH]

Hello Haskellers,

http://lpaste.net/119693

~~~
{-# LANGUAGE TemplateHaskell #-}

import Test.Tasty
import Test.Tasty.TH
import Test.Tasty.QuickCheck

main :: IO ()
main = defaultMain tests

tests = $(testGroupGenerator)

-- Problem 15
--
-- (**) Replicate the elements of a list a given number of times.
--
-- Example:
--
-- * (repli '(a b c) 3)
-- (A A A B B B C C C)
--
-- Example in Haskell:
--
-- >>> repli "abc" 3
-- "aaabbbccc"

prop_repli xs n = a && b
    where
        types = ((xs::[Int]), (n::Int))
        ys = repli xs n
        ys' = groupByN ys n
            where
                groupByN [] _ = []
                groupByN zs m = take m zs : groupByN (drop m zs) m
        a = and $ fmap ((==n).length) ys'
        b = and $ fmap f ys'
            where f (x:xs) = all (==x) xs

repli :: [a] -> Int -> [a]
repli [] _ = []
repli (x:xs) n
    | n <= 1 = (x:xs)
    | otherwise = repli' x n ++ repli xs n
        where
            repli' x' 0 = []
            repli' x' n' = x':repli' x' (n'-1)

~~~

> prop_repli xs n = a && b

If I set 'n' as ' n>=1', it's ok. But with just n, does not terminate.

Any advice would be appreciated.

Thanks.

-- 
YCH