I've decided on using Jest as my library of choice for unit and integration tests. A couple of really great and rather thorough articles helped me arrive at this decision, namely, this one and this one. I spent quite a bit of time browsing through the sites and codebase of several testing suites and I think for ease of use and comprehensiveness, Jest does all I might need at the moment. As far as functional testing goes ... I'm nowhere near that just yet, so I'm not going to worry about that right now. Little by little, I'm getting more comfortable with Mongodb as well, learning to update documents and fields and all of that fun stuff. I'll soon be setting up test databases that can be utilized and cleared with each test run. Little by little, I'm getting there.