# Cm Tdd

> Use when implementing any feature or bugfix. Routes to the core Red-Green-Refactor loop, test quality guidance, rationalization handling, examples, or stuck-state recovery.

- Skill: `tody-agent/cm-tdd` (Agent Skill, multi-file: 6 files)
- Install (CLI): `npx skillmds@latest add tody-agent/cm-tdd`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tody-agent/cm-tdd/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tody-agent (https://skillmd.com/u/tody-agent)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tody-agent/cm-tdd

---


# Test-Driven Development (TDD)

## TL;DR
- **Use when** writing or fixing code
- **Cycle**: Red → Green → Refactor
- **Rule**: no production code without a failing test first
- **Next**: `cm-execution` or `cm-code-review`

## When to Use
- new features
- bug fixes
- refactors
- behavior changes

## The Iron Law
```text
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
```

## Choose the Need

```
Need to execute the normal TDD loop?
└─ YES → Red-Green-Refactor

Need help designing or reviewing test quality?
└─ YES → Test Quality

Need to counter "skip TDD" rationalizations?
└─ YES → Rationalizations

Need a worked bug-fix example?
└─ YES → Bugfix Example

Are you blocked or unsure how to continue?
└─ YES → Stuck / Debugging
```

| Need | Summary | Load |
|---|---|---|
| Normal execution | core TDD loop and verification | `references/red-green-refactor.md` |
| Test quality | what good tests look like | `references/test-quality.md` |
| Reinforcement | anti-rationalization guidance | `references/rationalizations.md` |
| Example | concrete bug-fix walkthrough | `references/bugfix-example.md` |
| Recovery | how to proceed when stuck | `references/stuck-debugging.md` |

## Load Rules
- Load `red-green-refactor.md` for normal execution.
- Load `test-quality.md` when designing or reviewing tests.
- Load `rationalizations.md` only when the user or agent is trying to bypass TDD discipline.
- Load `bugfix-example.md` only for coaching or example use.
- Load `stuck-debugging.md` only when blocked.

## Non-Negotiables
- Watch the test fail before writing production code.
- Keep implementation minimal until green.
- Refactor only after green.
- Re-run verification after each meaningful change.

## The Bottom Line
**Write the failing test first. Pass it minimally. Refactor only after green.**