[FEATURE] Add testing

[lucasstarsz]

Is your feature request related to a problem? Please describe.

With situations like pull request #33, it is imperative that tests are run to ensure that the project works as expected.

Describe the solution you'd like

Add tests covering at least the most used features.

Describe alternatives you've considered

There are not many alternatives to consider -- testing a library is objectively the most effective way to ensure any part of it works as intended.