Add CI for automated testing

[trossi]

It'd be useful to have automated tests to ensure that codes keep working during development.

[MichalTorma]

that would be a dream. How do you imagine data prep testing though - it would be integration test on a small region? because we are relying on outside services so much...

[trossi]

I think it would be nice if we had a script to generate some small random data for testing (random values but correct data structures). Then having an integration test running through the steps would catch at least some issues (unit tests could be even better but more work with current code structure).