FWIW, I always write tests for my changes, as long as they have any impact on behaviour (i.e. not writing tests for adding a little logging or metrics, but am f

FWIW, I always write tests for my changes, as long as they have any impact on behaviour (i.e. not writing tests for adding a little logging or metrics, but am for any new or modified business logic). Every single dev having a strong commitment to automated testing is a requirement for an environment where you can sometimes get away without manual testing. For any changes where it's not obvious that it'll work in practice, despite the tests, I also run the full app locally, and test manually. Or for any UI changes, obviously. For backend changes, for some codebases, running the full app locally is required for ANY change, period - hard to reason about code, little-to-no type safety, weak overall test coverage, etc. But if you have a simple backend change in an easy to reason about code base, that has great guardrails (great automated test coverage, great monitoring/alerts, canary deploys with auto-rollback), there really is not much reason to actually run the full app for a simple change, which is a nice productivity boost. Just make the tweak, write/modify tests if necessary, and if everything passes on CI, you're good to go. For the 8 years before my current job, I was working in environments that weren't safe enough to do this ever, and was horrified when devs would merge without actually manually testing their changes. But my current company/environment has a codebase with strong typing and nice abstractions/local reasoning, great automated test coverage, and great monitoring/alerts and canary deploys with auto-rollback. Took me a bit, but I've embraced the "no need to run the app for simple changes" approach, and it works great in this environment - highly productive and still safe enough.