QuickCheck.hs

{-
Copyright (c) 2017 IOHK

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-- | Testing utilities to be used with QuickCheck

module Test.Util.QuickCheck
  ( ShowThroughBuild (..)

  -- * Roundtrip properties
  , roundtripTest
  , roundtripADTTest
  , roundtripTestSTB
  , aesonRoundtrip
  ) where

import Data.Aeson (FromJSON(..), ToJSON(..))
import qualified Data.Aeson as Aeson
import Data.Typeable (typeRep)
import Fmt (Buildable, pretty)
import Test.QuickCheck (Arbitrary, forAll, resize)
import Test.QuickCheck.Arbitrary.ADT
  (ADTArbitrary(..), ConstructorArbitraryPair(..), ToADTArbitrary(..))
import Test.Tasty (TestTree)
import Test.Tasty.QuickCheck (Property, testProperty, (.&&.), (===))
import qualified Text.Show (show)

import Michelson.Test.Util (roundtripTest)

----------------------------------------------------------------------------
-- 'Show'ing a value though 'Buildable' type class.
-- Useful because QuickCheck uses 'Show'.
----------------------------------------------------------------------------

newtype ShowThroughBuild a = STB
  { unSTB :: a
  } deriving newtype (Eq, Ord, Arbitrary)

instance {-# OVERLAPPABLE #-} Buildable a => Show (ShowThroughBuild a) where
  show = pretty . unSTB

instance Show (ShowThroughBuild ByteString) where
  show = show . unSTB

----------------------------------------------------------------------------
-- Roundtrip
----------------------------------------------------------------------------

-- | Version of 'roundtripTest' which shows values using 'Buildable' instance.
roundtripTestSTB ::
     forall x y err.
     ( Show (ShowThroughBuild x)
     , Show (ShowThroughBuild err)
     , Typeable x
     , Arbitrary x
     , Eq x
     , Eq err
     )
  => (x -> y)
  -> (y -> Either err x)
  -> TestTree
roundtripTestSTB xToY yToX = roundtripTest (xToY . unSTB) (bimap STB STB . yToX)

roundtripADTTest ::
     forall x y err.
     ( Show x
     , Show err
     , Typeable x
     , ToADTArbitrary x
     , Eq x
     , Eq err
     )
  => (x -> y)
  -> (y -> Either err x)
  -> TestTree
roundtripADTTest xToY yToX = testProperty typeName prop
  where
    prop :: Property
    prop =
      forAll (resize 1 $ toADTArbitrary (Proxy @x)) $ \adt ->
        foldr ((.&&.) . check . capArbitrary) z (adtCAPs adt)
    typeName = show $ typeRep (Proxy @x)
    check x = yToX (xToY x) === Right x
    z = True === True

aesonRoundtrip ::
     forall x. (Show (ShowThroughBuild x), ToJSON x, FromJSON x, Typeable x, Arbitrary x, Eq x)
  => TestTree
aesonRoundtrip = roundtripTestSTB (Aeson.encode @x) Aeson.eitherDecode