[Haskell-beginners] HUnit - testing for failed pattern match

[Edward Z. Yang]

What you describe is one of the cases when a partial function is ok
(though it's probably better to do something like:

giveMeThree x
| x == 3 = True
| otherwise = error "giveMeThree: not three"

It's frequently not possible, but if you can arrange your types so that
the invalid values are not possible, even better.)

Cheers,
Edward