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{-# LANGUAGE ScopedTypeVariables #-}
module Text.XmlHtml.TestCommon where
import Control.Exception as E
import System.IO.Unsafe
import Test.Framework
import Test.Framework.Providers.HUnit
import Test.HUnit hiding (Test, Node)
------------------------------------------------------------------------------
-- | Tests a simple Bool property.
testIt :: TestName -> Bool -> Test
testIt name b = testCase name $ assertBool name b
------------------------------------------------------------------------------
-- Code adapted from ChasingBottoms.
--
-- Adding an actual dependency isn't possible because Cabal refuses to build
-- the package due to version conflicts.
--
-- isBottom is impossible to write, but very useful! So we defy the
-- impossible, and write it anyway.
isBottom :: a -> Bool
isBottom a = unsafePerformIO $
(E.evaluate a >> return False) `E.catches` [
E.Handler $ \ (_ :: PatternMatchFail) -> return True,
E.Handler $ \ (_ :: ErrorCall) -> return True,
E.Handler $ \ (_ :: NoMethodError) -> return True,
E.Handler $ \ (_ :: RecConError) -> return True,
E.Handler $ \ (_ :: RecUpdError) -> return True,
E.Handler $ \ (_ :: RecSelError) -> return True
]
------------------------------------------------------------------------------
isLeft :: Either a b -> Bool
isLeft = either (const True) (const False)
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