Add more complicated tests

[charleskawczynski]

I tried #16 and I'm still seeing some failures: https://buildkite.com/clima/climacore-ci/builds/4513#01928b2f-bde4-4a90-9c65-906327d49369/6.

I think we need to add some (potentially broken) tests that exercise some more complex cases, so that we see fixes in real-world examples.