Just to walk the walk, and not just talk the talk, here's a quick unit
testing 'diff' driver I hacked up for QuickCheck.
When run, it 'diffs' (well, just prints ;-) the incorrect values from
the unit test:
$ runhaskell T.hs
sort unit test : Falsifiable after 0 tests:
- [1,2,3]
+ [1,3,2]
>From a normal QC specification like:
prop0 = (sort [3,2,1], [1,3,2])
main = mapM_ (\(s,a) -> printf "%-25s: " s >> a n) tests
where
n = 100
tests = [("sort unit test", mytest prop0)]
The full driver code is attached. It is just proof of concept, but you
can see how to extend it to be smarter/prettier.
Note that we actually probably want to use SmallCheck here, to prevent
bogus repetition of the test. (I.e. 500 tests all passed, for a unit test).
Note also, the driver would need further extending, since we've changed
the structure of the Testable values.
Cheers,
Don
import Data.List
import Text.Printf
import System.IO
import System.Random
import Test.QuickCheck
prop0 = (sort [3,2,1], [1,3,2])
main = mapM_ (\(s,a) -> printf "%-25s: " s >> a n) tests
where
n = 100
tests = [("sort unit test", mytest prop0)]
------------------------------------------------------------------------
-- And a custom driver that `diff's the output
mytest :: (Show a, Eq a) => (a,a) -> Int -> IO ()
mytest (a,b) n = mycheck defaultConfig
{ configMaxTest=n
, configEvery= \n args -> [] } a b
mycheck :: (Show a , Eq a) => Config -> a -> a -> IO ()
mycheck config a b =
do rnd <- newStdGen
mytests config (evaluate (a == b)) a b rnd 0 0 []
mytests :: (Show a , Eq a)
=> Config -> Gen Result -> a -> a -> StdGen -> Int -> Int -> [[String]]
-> IO ()
mytests config gen a b rnd0 ntest nfail stamps
| ntest == configMaxTest config = do done "OK," ntest stamps
| nfail == configMaxFail config = do done "Arguments exhausted after" ntest
stamps
| otherwise =
do putStr (configEvery config ntest (arguments result)) >> hFlush stdout
case ok result of
Nothing ->
mytests config gen a b rnd1 ntest (nfail+1) stamps
Just True ->
mytests config gen a b rnd1 (ntest+1) nfail (stamp result:stamps)
Just False ->
putStr ( "Falsifiable after "
++ show ntest
++ " tests:\n"
++ "- " ++ show a
++ "\n"
++ "+ " ++ show b
++ "\n"
) >> hFlush stdout
where
result = generate (configSize config ntest) rnd2 gen
(rnd1,rnd2) = split rnd0
done :: String -> Int -> [[String]] -> IO ()
done mesg ntest stamps =
do putStr ( mesg ++ " " ++ show ntest ++ " tests" ++ table )
where
table = display
. map entry
. reverse
. sort
. map pairLength
. group
. sort
. filter (not . null)
$ stamps
display [] = ".\n"
display [x] = " (" ++ x ++ ").\n"
display xs = ".\n" ++ unlines (map (++ ".") xs)
pairLength xss@(xs:_) = (length xss, xs)
entry (n, xs) = percentage n ntest
++ " "
++ concat (intersperse ", " xs)
percentage n m = show ((100 * n) `div` m) ++ "%"
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