Testing the Negative: Why Happy-Path Tests Lie

Your tests pass, your coverage is high, and your code still breaks in production. That’s what happens when you only test the happy path. In this episode, Matt and Robert take on one of Robert’s biggest pet peeves: unit tests that never cover the negative, or sad, path. They break down what the sad path actually is, why developers naturally skip it (code is written for the success case, negative tests feel like extra work, and coverage tools don’t tell the whole story), and where the gaps show up in production, from partial failures in multi-service architectures to untested catch blocks, else branches, early returns, retries, and fallbacks. They close on a practical note: with today’s tooling, including AI assistance, writing tests for both the positive and negative cases is easier than it has ever been. There’s no good excuse left. Watch this episode on YouTube: https://www.youtube.com/watch?v=PpQwkBuPxy8