Add tests to Github workflow

[LauJohansson]

I would recommend alter the Github workflow for the PRs to include a unittest run.
In this way, developers are ensured that the code works as expected before merging (at least the tests should succeed).

Describe the solution you'd like
Simply add a new Github action that runs something similar with this:

python -m pytest /tests/

Reach out to me if you need assistance :)