Arbitrary instances for exceptions?

[kindaro]

Arbitrary instances for exceptions are trivial but tedious to define. Someone has already done the work in text-show package tests, why do we not publish this so that it is reusable?

It would be useful when checking code that manages exception handling. IO code may be mocked in Catch monad and tested for exception resilience. I am actually doing this somewhere even now.

[kindaro]

Actually the code at the link is not fit for use cases where arbitrary :: Gen SomeException should generate all kinds of exceptions. At that link, it is defined thusly:

instance Arbitrary SomeException where
    arbitrary = SomeException <$> (arbitrary :: Gen AssertionFailed)

— So it will only ever generate failed assertions. The more reason to create a more "varied" generator!