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96 lines
3.8 KiB
Haskell
96 lines
3.8 KiB
Haskell
{-# LANGUAGE GADTs, TypeFamilies #-}
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module Test.Hspec.LeanCheck
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( prop
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, forAll
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) where
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import Control.Exception
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import Data.Bifunctor (first)
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import Data.List (intercalate)
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import Data.Maybe (listToMaybe)
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import Data.Typeable
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import GHC.Show as Show (showsPrec)
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import Test.Hspec
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import Test.Hspec.Core.Spec as Hspec
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import qualified Test.HUnit.Lang as HUnit
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import Test.LeanCheck.Core
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data Property where
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Property :: IOTestable prop => prop -> Property
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-- | Perform an enumerative test of a property using LeanCheck.
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--
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-- 'prop' will typically be a function of one or more 'Listable' arguments, returning either 'Bool' or 'IO ()' (in the latter case, typically via 'shouldBe' and friends). For example:
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--
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-- > describe "+" $ do
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-- > prop "associativity" $
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-- > \ a b c -> a + (b + c) `shouldBe` (a + b :: Int) + c
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prop :: (HasCallStack, IOTestable prop) => String -> prop -> Spec
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prop s = it s . Property
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data ForAll a where
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ForAll :: IOTestable prop => [[a]] -> (a -> prop) -> ForAll a
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-- | Test a property given by an explicit list of tiers rather than a 'Listable' instance. This can be used to e.g. filter input values for which the property does not hold.
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--
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-- > describe "mean" $ do
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-- > prop "≥ the minimum" . forAll (not . null `filterT` tiers) $
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-- > \ list -> (mean list :: Int) `shouldSatisfy` (>= min list)
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forAll :: IOTestable prop => [[a]] -> (a -> prop) -> ForAll a
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forAll = ForAll
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instance Example Property where
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type Arg Property = ()
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evaluateExample (Property prop) (Params _ bound) _ _ = do
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result <- try (iocounterExample bound prop)
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case result of
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Left e
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| Just (LeanCheckException messages e') <- fromException e -> throw (addMessages messages e')
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| otherwise -> throw e
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Right (Just messages) -> pure $ Result "" (Failure Nothing (Reason (concat messages)))
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Right Nothing -> pure $ Result "" Success
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where addMessages messages (HUnit.HUnitFailure loc r) = HUnit.HUnitFailure loc $ case r of
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HUnit.Reason s -> HUnit.Reason (intercalate "\n" messages ++ "\n" ++ s)
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HUnit.ExpectedButGot Nothing expected actual -> HUnit.ExpectedButGot (Just (concat messages)) expected actual
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HUnit.ExpectedButGot (Just preface) expected actual -> HUnit.ExpectedButGot (Just (intercalate "\n" messages ++ preface)) expected actual
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class IOTestable t where
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-- 'resultiers', lifted into 'IO'.
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ioResultTiers :: t -> [[IO ([String], Bool)]]
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instance IOTestable (IO ()) where
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ioResultTiers action = [[ (action >> pure ([], True)) `catch` (throw . LeanCheckException []) ]]
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instance (IOTestable b, Show a, Listable a) => IOTestable (a -> b) where
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ioResultTiers p = concatMapT (resultiersFor p) tiers
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instance IOTestable Bool where
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ioResultTiers p = [[ pure ([], p) ]]
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instance Show a => IOTestable (ForAll a) where
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ioResultTiers (ForAll tiers property) = concatMapT (resultiersFor property) tiers
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resultiersFor :: (IOTestable b, Show a) => (a -> b) -> a -> [[IO ([String], Bool)]]
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resultiersFor p x = fmap (eval x) <$> ioResultTiers (p x)
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eval :: Show a => a -> IO ([String], Bool) -> IO ([String], Bool)
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eval x action = first (prepend x) <$> action
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`catch` \ (LeanCheckException messages failure) -> throw (LeanCheckException (prepend x messages) failure)
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where prepend x = (showsPrec 11 x "":)
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-- | 'counterExamples', lifted into 'IO'.
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iocounterExamples :: IOTestable a => Int -> a -> IO [[String]]
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iocounterExamples n = fmap (fmap fst . filter (not . snd)) . sequenceA . take n . concat . ioResultTiers
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-- | 'counterExample', lifted into 'IO'.
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iocounterExample :: IOTestable a => Int -> a -> IO (Maybe [String])
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iocounterExample n = fmap listToMaybe . iocounterExamples n
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data LeanCheckException = LeanCheckException [String] HUnit.HUnitFailure
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deriving (Show, Typeable)
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instance Exception LeanCheckException
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