Get to 100% test coverage

[devrelm]

The project is currently up around 90% code coverage. While code coverage is not an entirely reliable metric of code quality, there's not much reason that a small library such as this shouldn't be at 100%.

Add meaningful tests to reach 100% code coverage.

[devrelm]

#10 (TypeScript Rewrite) introduced some issues with calculating coverage due to the map files not making it all the way to the dist directory. We'll want to fix that first before (or as part of) tackling this issue.