[#1505] Merge tests that verify that the user was invited and it is pending

This is a tiny compromise in readability (IMO) to make the tests a bit faster
[#1505] Test not only the method call, but also that we're returning the value
[#1505] Test for actual True-ness, and not truthiness.

If we don't add the ```is True```, any truthy value works (i.e. 'string').