Thanks a lot for the PR!

I'll have to set up Wikibase and get the tests to work on my machine again, so it might take me a while to review this :)

Alright, I've set up the testing environment again. Your code unfortunately isn't working yet.

I've now simplified the local setup guide a lot, this should get it to work on your device, too:https://wikibase-api.readthedocs.io/en/latest/development/development.html. Please let me know if I can provide more details :)

In case you get errors about duplicate items when running the tests, this might be because of a previously failed test run which didn't clean up its data properly. Creating a new Docker volume should do the trick.