we should only remove the method once! as we only inject once!
just remember what we have injected, much simpler
we would only have one injected defi actually
clear the session upon reset
move mock/stub/etc into session; any_instance_of needs a map as well
more tests
this test reveals that we need to remember the very original method!
yet another test for any_instance_of
prepare 0.5.1 release