In the summer, while I was working on a feature locally, I noticed a test started failing. I initially dismissed it: I assumed there was some flakiness, and CI was green, so everything must’ve been good, right? Until it kept failing, only locally. A test that a few days before was working as normal. It was not just a single test. Multiple tests were failing, so the immediate thought was that they must be related. The question was: why are they failing on my machine, but not on CI? The exact same code, the exact same setup — or so...