Change Details

This is a parent story for couple of smaller iterations that aim at improving what and how tests are being written and ran in Wikibase extension. The goals are: * significantly decrease the amount of time our browser tests need to run * significantly decrease the flakiness in our browser tests * improve the clarity, structure and utility of the separation between unit, integration and crucial e2e product tests (those are usually browser tests for web ui, and api tests for apis). Possible 1st-level break-down: 1. write e2e crucial happy path(s) tests for Wikidata web ui and api. 2. reduce the amount of browsers tests, converting (most of) them into: * UI components unit and integration tests * API integration tests * more unit and integration tests in the backend