I'm not saying don't unit test or that E22 tests don't have disadvantages, but... end-to-end tests are not frontend tests, so they will still catch problems reg

I'm not saying don't unit test or that E22 tests don't have disadvantages, but... end-to-end tests are not frontend tests, so they will still catch problems regardless of whether the frontend changes. Unless you are changing something that doesn't affect any features (in which case, why it is in the codebase?), an end-to-end test could possibly catch it.