Writing code with tests first: RED-GREEN-REFACTOR, reproduce bugs as failing tests before fixing, and avoid testing anti-patterns. Use when implementing behaviour, fixing a defect, or asked to add tests.
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What the file says
# Test-driven development
Iron law: no production code without a failing test that demands it.
## The cycle
1. **RED**: write the smallest test for the next bit of behaviour. Run it. Read the failure and confirm it fails for the reason you intended (your assertion), not an import error, a typo, or a missing fixture. A test that fails for the wrong reason proves nothing.
2. **GREEN**: write the least production code that passes. Run the test again. Nothing more than the test asks for.
3. **REFACTOR**: improve names and structure while all tests stay green. Run them again.
Then the next slice. Cycles are minutes, not hours; commit-sized.
## Bugs: reproduce first
- Turn the bug into a failing test before touching the fix. Watch it fail, fix, watch it pass.
- If you cannot express the bug as a failing test, you do not understand it yet; switch to `skill://systematic-debugging`.
- Keep the repro test after the fix as the regression test. A bug fix without a test that dies when the bug returns is incomplete.
## Already wrote the code? Delete it
…
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GET https://markdownregistry.com/api/v1/resolve?ref=damianvtran/local-operator/test-driven-development
GET https://markdownregistry.com/api/v1/blob/516707d441ae66c3a49b2385dc1f47916593cf67a0a2f4a738807dde38ecd5a0
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