I dunno, in my career I’ve found that UI e2e tests were the ones that actually found bugs. All the unit tests that I’ve written ware mostly ceremony, to increas

I dunno, in my career I’ve found that UI e2e tests were the ones that actually found bugs. All the unit tests that I’ve written ware mostly ceremony, to increase code coverage, etc, and were the first to need refactoring after some code change. A lot of refactoring. The tests that stayed true were the UI tests that almost always pointed to real problems with real code. It took a while to figure out how to write them though - trying to rely as little as possible on the internal ids / html / css and write them with what the user sees - e.g. instead of clicking on the button with “testid=login” we would “click on the button with the text login in it”. Identifying fields by the labels to them or tables by their column headers. It was inspired by rails’ capibara testing lib. And making sure the tests were not flaky, fast to execute and isolated took some time. But it was so worth the investment - it’s surprising how little those tests would change, as it allowed us to fearlessly refactor stuff without changing any tests. They felt a lot more like a friendly QA helping out rather than an annoyance you had to deal with after you’ve finished writing your code. And writing them was actually fun, since you didn’t have to understand how the app worked, fiddle with brittle css identifiers etc, you just wrote the steps you thought the user should do and saved it into a file. Being UI tests kinda meant they tested the whole system with the various micro services involved, databases and other infra. And I think this is where most problems in software arise, at the edges of systems when they try to interact with each other. Static types, immutability automatic API schemas and validators usually make sure the code one writes executes reasonably well, its where the code one writes starts interacting with all the other systems where people usually can’t anticipate things. And thats where the integration / e2e / UI tests help the most I think.