Write some tests for the toy environments

[david-lindner]

Tests are great!

[jvmncs]

Looks like there were some unit tests merged in #14. Seems like a good start, but we'll also want to write some integration tests for safe-grid-agents and this one. Mainly, we'll want to test that changes here don't introduce breaking changes with what we do over there. Could be as simple as a single training/evaluation iteration of Q learning on each of the environments

[david-lindner]

I think the additions from #17 are fine as unittests for the toy environments.

Integration tests between the repos make a lot of sense! Just to clarify how you imagine this: We would add tests to this repo, that import safe-grid-agents, run a training and evaluation iteration and check that nothing crashes and something reasonable happens, correct?

[jvmncs]

Precisely! That seems sufficient for now, at least until we have better unit testing over there.