Your AI's tests pass. That doesn't mean the code works.

You ask a coding agent to fix a bug. It writes the code, writes the tests, CI goes green, you merge. The bug's still there.

The agent's job was to turn the check green. The honest way to do that is to fix the code. The lazy way is to write a test that passes no matter what the code does. CI can't tell those two apart. A green check means the tests passed, not that the code is right.

It's easy to miss in review, because the test sits right there looking like proof:

test("parses the config", () => {

const result = parseConfig(rawInput);