# Workflow Tdd

> Test-first engineering workflow for implementation and issue handling. Use for building features, fixing bugs, handling regressions, or reproducing issues before changing code. Triggers on: implement, build feature, issue, bug fix, regression, failing test, test first, tdd.

- Skill: `yuangjay/workflow-tdd` (Agent Skill)
- Install (CLI): `npx skillmds@latest add yuangjay/workflow-tdd`
- Raw SKILL.md: https://api.skillmd.com/api/skills/yuangjay/workflow-tdd/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Productivity
- Author: yuangjay (https://skillmd.com/u/yuangjay)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/yuangjay/workflow-tdd

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# Workflow TDD

## Purpose

Apply a strict test-first loop to implementation and bug-fix tasks.

## Mandatory Loop

1. Reproduce first:
   - If an issue is reported, add or update a focused test that demonstrates the current failure.
   - If no test exists, create the narrowest failing test that captures the expected behavior.
2. Implement second:
   - Make the smallest code change that turns the focused test green.
3. Verify third:
   - Run the focused test again.
   - Run the relevant broader suite to catch regressions.
4. Update process artifacts last:
   - Only update instructions, skills, or automation after the implementation and verification loop is green.

## Hard Rules

- No implementation without a failing test or an explicit reason the behavior cannot be tested.
- No commit while tests are red.
- When an issue changes expected behavior, the test case changes before the code change.
- Keep the first failing test small so debugging cost stays low.