Your AI Agent Says All Tests Pass. Your App Is Still Broken

How Knight Rider Testing Gave Me My Nights Back There is a moment every developer using AI coding agents knows well. You wake up, check your terminal, and see the beautiful green wall: 47 tests passed, 0 failed. You open the app. The button does nothing. The layout is sideways. The feature you asked for doesn't exist. The agent rewrote half the codebase, generated tests that validate its own hallucinations, and declared victory. You are back to square one, except now you also have to understand 2,000 lines of code you didn't write. I call this the Vibe Coding Death Spiral. You prompt, the agent codes, the agent tests, the agent passes, and nothing actually works. You correct it, and it "fixes" things by rewriting what was already working. The tests still pass because the tests were written by the same agent that wrote the broken code. It is like hiring someone who grades their own homework and wondering why they always get an A. After months of this cycle, I stopped asking how to write