Add unit tests

[Elia-238]

Please add unit tests so we can check if the project works.

[seapagan]

Definitely 😁!
It's on the roadmap, and I'm slowly adding them to a derivative project of this template at the moment. I'll backport them to this project when that's done.

It will probably be a couple of weeks, realistically.

[seapagan]

I merged PR #84 today.
This brings the coverage up to 80%. A few fixes and refactoring were also involved in this PR that came to light while writing the testing, so I thought it better to merge. The PR also includes a GitHub Action to run the tests on each commit or PR

I'll leave this Issue open until full coverage is reached 👍

[seapagan]

@Elia-238 Unless you have any issues Im going to close this PR.

Coverage is up to 98% with both Unit and Integration tests. The last 2% is in the startup connection-testing code and I need to re-write those tests as they are causing other tests to fail (the mock is not being cleared). All the important logic is tested though.

[seapagan]

Closing as test coverage is at 98%