Test First by Evidence

Core principle. A test you did not watch fail proves nothing. It might test the wrong thing, and you would never know.

• Keep hypotheses and proof separate. Debugging may use recorded incidents and controlled experiments before a local occurrence. Implementation starts from a test that exposes the relevant defect or missing behaviour, not necessarily the whole incident.
• The weight sits in Watch it fail. Everything else is what to do once the red is real.
• You opened this in the middle of something. This is how to do that work, not a replacement for it. Name what you were doing before you start, and return to it when this is done.

The law

NO PRODUCTION CODE WITHOUT A TEST YOU WATCHED FAIL

• Code written before its test is unproven, and gets re-derived from a red rather than wrapped in a test that passes immediately.
• Make it recoverable before removing anything. Discarding work the human has not agreed to discard is not yours to do.
• A test that passes the first time you run it is not a test yet. It describes what the code already does.
• A test that errors is not a red. An error is a broken test; a failure is a working test with nothing to satisfy it.