aroundAll.hs

aroundAll :: forall a. ((a -> IO ()) -> IO ()) -> SpecWith a -> Spec
aroundAll withFunc specWith = do
  (var, stopper, asyncer) <- runIO $
    (,,) <$> newEmptyMVar <*> newEmptyMVar <*> newIORef Nothing
  let theStart :: IO a
      theStart = do

        thread <- async $ do
          withFunc $ \x -> do
            putMVar var x
            takeMVar stopper
          pure $ error "Don't evaluate this"

        writeIORef asyncer $ Just thread

        either pure pure =<< (wait thread `race` takeMVar var)

      theStop :: a -> IO ()
      theStop _ = do
        putMVar stopper ()
        traverse_ cancel =<< readIORef asyncer

  beforeAll theStart $ afterAll theStop $ specWith