test-driven-development
TDD: enforce RED-GREEN-REFACTOR, tests before code.
npx skills add HezaoHezao/poirot --skill test-driven-development --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# Test-Driven Development (TDD) ## Overview Write the test first. Watch it fail. Write minimal code to pass. **Core principle:** If you didn't watch the test fail, you don't know if it tests the right thing. ## When to Use **Always:** - New features - Bug fixes - Refactoring - Behavior changes **Exceptions (ask the user first):** - Throwaway prototypes - Generated code - Configuration files Thinking "skip TDD just this once"? Stop. That's rationalization. ## The Iron Law ``` NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST ``` Write code before the test? Delete it. Start over. **No exceptions:** - Don't keep it as "reference" - Don't "adapt" it while writing tests - Don't look at it - Delete means delete Implement fresh from tests. Period. ## Red-Green-Refactor Cycle ### RED — Write Failing Test Write one minimal test showing what should happen. **Good test:** ```python def test_retries_failed_operations_3_times(): attempts = 0 def operation(): nonlocal attempts attempts += 1 if attempts < 3: raise Exception('fail') return 'success' result = retry_operation(operation) assert result == 'success' assert attempts == 3 ``` Clear name, tests real behavior, one thing. **Bad test:** ```pyt
- Overview
- When to Use
- The Iron Law
- Red-Green-Refactor Cycle
- RED — Write Failing Test
- Verify RED — Watch It Fail
- GREEN — Minimal Code
- Verify GREEN — Watch It Pass
- REFACTOR — Clean Up
- Repeat
- Avoid Horizontal Slices
- Why Order Matters
- Common Rationalizations
- Red Flags — STOP and Start Over
pytest tests/test_feature.py::test_specific_behavior -v Run the specific test Then run ALL tests to check for regressions pytest tests/ -q
What does the test-driven-development skill do?
TDD: enforce RED-GREEN-REFACTOR, tests before code.
How do I install it?
Run `npx skills add HezaoHezao/poirot --skill test-driven-development --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From HezaoHezao/poirot, a repository with 139 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.