This was a vestige from when we used to need the unittest2 library for pre-2.7
compatibility. Now that we require Python 2.7, we aren't using that library
and this indirection wasn't doing any good.
- Fix `test_event_X` name collision between tests causing tests to
fail unexpectedly.
- Update tests to match new hook plugin design (i.e. remove shell and
subtitution option testing).