assertAst s ast = case parseString (s ++ "\n") of
    Left err          -> assertFailure $ show err
    Right dockerfile  -> assertEqual "ASTs are not equal" ast $ map instruction dockerfile
assertAst s ast = case parseString (s ++ "\n") of
    Left err          -> assertFailure $ show err
    Right dockerfile  -> assertEqual "ASTs are not equal" ast $ map instruction dockerfile
assertAst s ast = case parseString (s ++ "\n") of
    Left err          -> assertFailure $ show err
    Right dockerfile  -> assertEqual "ASTs are not equal" ast $ map instruction dockerfile