fix broken tests, refactor for testability

[chuckadams]

After #19 was merged, most tests are now broken. Some can be removed because they test systems that no longer exist, but others can be rescued.

I'd also like to see more tests in general, and more of them be unit tests rather than integration. Ideally we want to just test inputs and outputs, not have to "mock around the clock". We needn't be gentle about it either: if code needs to be refactored to make testing easier, then so much the better for the code in the long run.