Is there an assertException in any of the Haskell test frameworks?
I'm writing some tests using HUnit and I would like to assert that a particular function throws an exception given a certain input. I can't find an assert function which provides the required functionality. Anyone know of a test framework that does?
Although HUnit doesn't come with any exception assertions, it's easy to write your own:
import Control.Exception
import Control.Monad
import Test.HUnit
assertException :: (Exception e, Eq e) => e -> IO a -> IO ()
assertException ex action =
handleJust isWanted (const $ return ()) $ do
action
assertFailure $ "Expected exception: " ++ show ex
where isWanted = guard . (== ex)
testPasses = TestCase $ assertException DivideByZero (evaluate $ 5 `div` 0)
testFails = TestCase $ assertException DivideByZero (evaluate $ 5 `div` 1)
main = runTestTT $ TestList [ testPasses, testFails ]
You can do something more fancy like using a predicate instead of explicit comparison if you like.
$ ./testex
### Failure in: 1
Expected exception: divide by zero
Cases: 2 Tried: 2 Errors: 0 Failures: 1
Note that evaluate here might get optimized away (see GHC ticket #5129), but for testing code in the IO monad this should work fine.
你可以使用testpack中的assertRaises 。
hspec（或者更准确地说是hspec-expectations）已经shouldThrow 。