Implement tests for existing functions

This package currently has almost no unit testing. I think we need to implement tests for all of the existing functionality. Moving forward, I think we should require that any new functionality must come with associated tests.

This will be easier to enforce once we have github Actions up and running

No files, entry points, or existing tests are named. Start by inventorying the package's existing functionality and current test layout, then determine the scope needed to cover it. Done would mean the existing functionality has associated unit tests and the future testing expectation is defined; GitHub Actions is mentioned as a later enforcement path.

Written by the indexing model from the issue text.