The platform team does do code review and automated tests, but occasionally something slips through, so they QA release branches as well. Is there any major ap

The platform team does do code review and automated tests, but occasionally something slips through, so they QA release branches as well. Is there any major app (say, at least 1 million SLOC) which has such good automated tests that they're comfortable shipping master without any manual QA? I'd be really surprised if there is. Even if a team is totally committed to automating all their testing, there are some big challenges with doing so at scale: - You run into all kinds of rare bugs (with AOSP, the emulator, host OS, etc.). When I worked at Square our biggest app had ~5 hours of automated tests, and these rare bugs made it very hard to keep our builds stable. I imagine thoroughly testing AOSP would take an order of magnitude longer. - If you want to test on a variety real phones (which seems critical for AOSP), then testing every master commit is cost prohibitive. - It's hard to automatically detect graphical glitches. You can take screenshots at certain times and validate that they're pixel perfect, but you might still miss a glitch in between screenshots, e.g. during an animation.