add a few potential tests for the pwdSimulator

Second verse, same at the first:

Sorta WIP. (In other words: the simulator is still marinating in my brain, and I may think of more and/or reconsider these tests.)

First two tests I added might be more for points of discussion, but I believe the third (re: settings change during a run of scheduled basals), which currently fails, poses more of a problem.

Whenever you're ready to discuss @cheddar @kentquirk
Er, there would have to be an additional assumption that the mythical device I'm talking about also doesn't do a good job of keeping track of your current active schedule (in order to have this situation of schedule mismatch come up). But that's very much not outside the realm of possibility; I believe @kentquirk told me the Omnipod doesn't keep an adequate history of your active basal schedule.