I fought exactly this battle for two years on my second team at Facebook. Never got very far TBH. Part of the reason is the "become a member of the tribe first"

I fought exactly this battle for two years on my second team at Facebook. Never got very far TBH. Part of the reason is the "become a member of the tribe first" thing that others have mentioned, but there's a kicker: any variance from the existing attitude about tests will itself tend to make you an Outsider. Here are some suggestions for things you can do to gently and slowly nudge things toward a better place. * Make sure your own changes are properly tested. * Make sure existing tests are reliable and quick to run, since these are common excuses for not doing more. * Develop tooling to make writing tests easier, or to write new kinds of tests. Key word is "new" because that taps into the neophilia that's endemic at these places. * Use new techniques to reliably reproduce bugs that are still fresh in people's minds, and to show how this can find related bugs as well. Don't spend too much time on any of these things, though. That will reduce your recognized "impact" and slow the process of gaining trust from the tech-lead "guardians of culture" who have usually decided (based on a mere 5-10 years' experience at only one company) that their current approach is perfect. Better to maximize that impact and then start promoting change. So, to a large extent, "drink the Kool Aid and shut up" really is the best approach available.