@tamird - great! I’m afraid I don’t have much advice for testing. I would add a bunch of unit tests (which are currently missing). Beyond that, it should be possible to write system tests by setting up an HTTP client and sending API calls and testing the results are expected. You would need some known test data, rather than the live data (maybe even have a test repo to store data in so it is a full end to end test).
If you have any questions, you can ping me on irc.