feat: add tests (wip)

[aarondill]

These use plenary's busted-like testing framework

As such, they require that plenary is installed to run.

Note: this is not a dependency for normal runtime.

Should I add a CI check that requires all tests are passing?

[aarondill]

@amirbilu is this something you're willing to pursue, or is it not worth putting my effort into?

[aarondill]

Please note that the current goal of the implemented tests is not to ensure that methods work right (as I've discovered and documented several bugs), but to match the current state of the codebase. This way, when a change is made, it can be quickly tested to ensure that it doesn't break anything else.

[amirbilu]

@aarondill this is indeed interesting

[aarondill]

I haven't had the opportunity to work on this recently due to real life things. I'll continue to work on this when I can, but I would appreciate contributions if you'd like to accelerate the process.