[Haskell-beginners] How to test "error"?

[Hilco Wijbenga]

Hi all,

I have a function that may call "error" if the input represents a bug
in my program. (Think something like PositiveInt -1; this should never
happen so Maybe or Either are not applicable.)

f :: Whatever
f = error "This should never happen."

spec :: Spec
spec =
    describe "f" $
        it "error" $
            return f `shouldThrow` anyErrorCall

The above does not work, I get "did not get expected exception:
ErrorCall". Using "anyException" doesn't work either.

How can I write a test for this? And (assuming I can get the test to
work), how do I check that the error message is indeed what I expect?

Cheers,
Hilco