# Tdd

> Use when the user wants regression-first or test-first scaffolding before implementation work expands.

- Skill: `justinedevs/tdd` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add justinedevs/tdd`
- Raw SKILL.md: https://api.skillmd.com/api/skills/justinedevs/tdd/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: JustineDevs (https://skillmd.com/u/justinedevs)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/justinedevs/tdd

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# TDD

Use this skill inside Codex when implementation should start by locking behavior with tests. `tdd` is a non-gating helper skill that supports execution once the relevant lane is ready.

## Output

Produce:
- behavior to lock
- minimal regression or failing test shape
- implementation boundary
- proof that the test belongs to the requested change
- exact next trigger, usually the implementation lane or `$cleanup`

## Rules

- Prefer the smallest failing test that proves the requested behavior.
- Lock current behavior before cleanup or refactor work when behavior is not already protected.
- Do not treat `tdd` as a replacement for the build gate.
- Keep test intent explicit so the next implementation step stays narrow.