Unit testing of the GUI

[lukasc-ubc]

Can you please implement some unit testing for the GUI?

Perhaps this? https://github.com/jmcgeheeiv/pyqttestexample/

https://stackoverflow.com/questions/15044447/how-do-i-unit-testing-my-gui-program-with-python-and-pyqt

Please make sure the test can run in headless more on GitHub Actions.
https://stackoverflow.com/questions/60692711/cant-create-python-qapplication-in-github-action