测试用例assertException

Ionut 发表于 Dev

爱奥努特

我正在尝试测试一个函数是否抛出某个异常。
我发现这个答案女巫是这样做的：

import Control.Exception
import Control.Monad
import Test.HUnit

assertException :: (Exception e, Eq e) => String -> e -> IO a -> IO ()
assertException preface expected action =
    handleJust isWanted (const $ return ()) $ do
        action
        assertFailure msg 
  where
    isWanted = guard . (== expected)
    msg = preface ++ "\nexpected exception: " ++ show expected

testPasses = TestCase $ assertException "Test1" DivideByZero (evaluate $ 5 `div` 0)
testFails  = TestCase $ assertException "Test2" DivideByZero (evaluate $ 5 `div` 1)

main = runTestTT $ TestList [ testPasses, testFails ]

女巫在奔跑时显示：

### Failure in: 1
Test2
expected exception: divide by zero
Cases: 2  Tried: 2  Errors: 0  Failures: 1

但assertException不会显示实际的异常或没有异常

有没有办法能够显示实际的异常或缺失？
我尝试用包装动作，catch但是我不知道如何将实际的异常传递给msg。

埃里克

这是一种实现方法：

{-# LANGUAGE ScopedTypeVariables #-}

import Control.Exception
import Control.Monad
import Test.HUnit
import GHC.Natural

assertException4 :: (Exception e, Eq e) => String -> e -> IO a -> IO ()
assertException4 preface expected action = do
  r <- catches
          (action >> return (Just "no exception thrown"))
          [ Handler (\e -> return $ if e == expected
                                       then Nothing
                                       else Just ("wrong exception thrown, expected " ++ show expected ++ ", got: " ++ show e))
          -- see the comments below about these two handlers:
          , Handler (\e -> throw (e :: AsyncException))
          , Handler (\(e::SomeException) -> return $ Just ("some other exception thrown: " ++ show e))
          ]
  case r of
    Nothing  -> return ()
    Just msg -> assertFailure (preface ++ ": " ++ msg)

test1 = TestCase $ assertException4 "Test1" DivideByZero (evaluate $ 5 `div` 0)
test2 = TestCase $ assertException4 "Test2" DivideByZero (evaluate $ 5 `div` 1)
test3 = TestCase $ assertException4 "Test3" DivideByZero (evaluate $ [1,2,3] !! 4)
test4 = TestCase $ assertException4 "Test4" DivideByZero (evaluate $ (fromInteger (0 - 3) :: Natural) )

main = runTestTT $ TestList [ test1, test2, test3, test4 ]

四个测试用例是：