add unit testing

[garv-shah]

title says it all, things can break very easily when new features are added, and a lot of bugs being introduced is a result of this
unit testing would help catch these bugs before they go to production, so it's easier to maintain the repository with others
this being said, it's a lot of effort, and I'll probably only do it if other people start working on the project, or if I'm actively working on it (which I don't intend to do, I intend to fix these current bugs and stop working on the project), so maybe eventually, but not for now