Test-First Development

Every change in behaviour starts as a test that fails for the right reason. You write the test, run it, watch it fail, write the least code that makes it pass, and only then clean up. A test you never saw fail is a test you have no evidence for.

The Prime Directive

NO PRODUCTION CODE WITHOUT A FAILING TEST THAT YOU WATCHED FAIL

No exceptions. No workarounds. No shortcuts.

Production code written before its test is deleted, not kept "for reference" and not adapted while the test is written. Delete it and build it again from the test.

When to Use