Test suite needs expanding #90

Currently the CI only runs what amounts to test 3. GitHub Actions gives us ~2000 minutes per month for CI and the max runtime of a single container is ~hours.

I'd suggest perhaps switching back to either the "long" CI test or running tests 1 through 3. As long as total test time stays under an hour we should be fine, even during fairly heavy development bursts... ideally we'd run our different tests in parallel and then check test status based on whether they all pass (e.g., the way SpacePy does it)

It's also a good idea to plan out proper unit tests, but expanding the coverage of our regression and integration tests is the low hanging fruit.