Insufficient tests

[dominikcedro]

Last updates in /tests directory are from 8 years ago.
This fact greatly limits user confidence in stability of the project.
Since I personally do not have access to any Commcell instance, therefore I cannot see if those tests even pass.
I did not see any issues open on this topic.

I suggest:

1. Switching to Pytest.
2. Checking coverage of current tests.
3. Accordingly, expanding the test suite (with unit, e2e) for possible uncovered scenarios.
4. Utilising Github Actions with some simple test pipeline to monitor the status of the repository.

I'm interested in your take on this, maybe there is something I missed.
I will be more than happy to contribute.