Red-Green-Proof

A bug is not fixed because the tests pass. A bug is fixed when a test fails without your fix and passes with it, and you have watched it do both.

Overview

Use this skill when a bug, incident, flaky test, or unproven regression test is under investigation. It applies a strict red-green-red loop: establish the cause, observe a focused test fail, make the smallest fix, then remove the fix and observe the test fail again. The final revert is the proof that the test is actually coupled to the defect.

Workflow

Keep evidence for each phase separate. A test command that exits zero is not evidence that it exercised the defect; record the assertion and the observed failure or success. Do not proceed when the current phase is unobserved.