None of this stuff is really a function of the constructor.  I know that the prevailing style in this fail does it the way you've written, but I think it'd be worth starting to migrate this stuff to more modern style, particularly as we add code like this PR does.  In this case, I think you want to describe the "talkilla.login-success event" behavior.

As part of that, having an "and" in the predicate is often a tip off that you actually want two separate tests (which I think you do here), which becomes easier if you do this in its own describe() block.