what deserves a test, what does not, and how you know the suite is telling you the truth. Coverage percentages answer none of that. Written after an answer that was a number and nothing else. Updated October 2026. 7 min read Where the tests should live end to end, few integration unit, many and fast WHAT THEY ASK what would you test here? what would you not test? how do you test the failure? what makes a test flaky? The short version: say what you would test and what you deliberat...