Clean up tests

[willnorris]

I wrote most of the tests for this package, and even I have trouble following what they're actually doing, much less have confidence that they're actually covering all of the cases that we care about. I don't have a lot of immediate ideas for what needs to happen, though using better type and field names is probably a good start.

[willnorris]

done in 1edf4fb and subsequent commits.