foo :: Monad m => m Int
foo = fail "nope"

spec :: Spec
spec = do
  describe "foo" $ do
    it "does not work, heatsink (I)" $ do
      let res :: Either String Int
          res = foo
      res @?= Left "nope"
      --uncaught exception: ErrorCall (nope)
    it "does not work, heatsink (II)" $ do
      let res :: Either String Int
          res = foo
      return res `shouldReturn` Left "nope"
      --uncaught exception: ErrorCall (nope)
    it "works!" $ do
      let res :: Maybe Int
          res = foo
      res `shouldBe` Nothing
    it "this does not work" $ do
      let res :: Either String Int
          res = foo
          exp :: Either String Int
          exp = Left "nope"
      res `shouldBe` exp
      -- uncaught exception: ErrorCall (nope)
    it "this does not work either..." $ do
      let res :: Either String Int
          res = foo
      return res `shouldThrow` anyException
      -- did not get expected exception: SomeException
    it "...neither this" $ do
      let res :: Either String Int
          res = foo
      return res `shouldThrow` errorCall "nope"
      -- did not get expected exception: ErrorCall
    it "...nor this" $ do
      let res :: Either String Int
          res = foo
      return res `shouldThrow` anyErrorCall
      -- did not get expected exception: ErrorCall