Use test-driven development for behavior-changing feature or fix work, and whenever the user mentions TDD, test-first, red-green-refactor, tracer bullets, integration tests, or public-interface behavior tests. Skip for docs-only, path-only rename, formatting-only, or purely mechanical chores unless explicitly requested.
Install
npx skills add youdotcom-oss/agent-skills --skill tddnpx skills add youdotcom-oss/agent-skills --skill tdd -a claude-code -gnpx skills add youdotcom-oss/agent-skills --skill tdd -a codex -ggemini skills install https://github.com/youdotcom-oss/agent-skills.git --path .agents/skills/tddgh skill install youdotcom-oss/agent-skills tddgit clone --depth 1 https://github.com/youdotcom-oss/agent-skills /tmp/youdotcom-oss__agent-skills
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/youdotcom-oss__agent-skills/.agents/skills/tdd ~/.claude/skills/tdd # Claude Code
cp -R /tmp/youdotcom-oss__agent-skills/.agents/skills/tdd ~/.agents/skills/tdd # Codex, Cursor, Gemini CLI, Copilot, OpenCode