Let’s make a confession. This handbook is about me, and, I suspect, about you, your team, and your organization too.I’ve made almost every mistake listed in these pages. I’ve seen them repeated in startups, enterprise systems, and everything in between, while mentoring teams, auditing architectures, or helping companies rediscover what testing is really for. The point isn’t to assign blame. It’s to hold up a mirror. Because the truth is, most of these mistakes are so common, you can probably spot a few right now; in your code, your team, or your last retrospective.When we talk about test failures or mistakes, the first thing that usually comes to mind is developers, missed edge cases, flaky tests, broken pipelines.