# Han Coding > Test Double's coding skills: build test-first, refactor under green tests, review your branch and trace bugs to their root cause. Han Coding is the coding layer of Han, Test Double's open-source suite of skills and agents for solo product engineers and small teams. Its skills write code test-first, refactor it under a green test suite, and review, explain, test and investigate it, sending specialist agents to cover each angle in parallel. What you can do with it - Build a feature test-first with /tdd: a red-green-refactor loop that won't touch production code until a test has been seen to fail - Restructure existing code with /refactor, re-running the full test suite after every small step - Review your branch with /code-review: findings marked CRIT, WARN or SUGG, with file and line references and suggested fixes - Get up to speed on unfamiliar code or a pull request with /code-overview, or a paced /code-walkthrough - Trace a bug to its root cause with /investigate, backed by numbered evidence, and have the planned fix challenged before you build it - Plan automated or manual tests, assess a module's architecture, design an API change, or write coding standards from your own code How to install it In Claude Code, run /plugin marketplace add testdouble/han, then /plugin install han-coding@han. It brings along han-core, whose shared specialist agents the skills dispatch, and han-communication. Install han@han instead for the whole Han suite. In Codex, add the marketplace with codex plugin marketplace add testdouble/han, then install han-communication, han-core and han-coding one by one, since Codex doesn't resolve dependencies. Good to know - /tdd and /refactor change code in your working tree; the other skills write a report or talk you through the code - The swarming skills scale how many agents they dispatch to the size of the job (small, medium or large) - Optional .han/config.md files set where reports are written and the default size - Open source under the MIT license, maintained by Test Double with best-effort support - Type: Skill - Made by: testdouble - Category: Developer tools - Formats: Skills, Claude plugins - Version: latest - Website: https://github.com/testdouble/han - Source: https://github.com/testdouble/han/tree/HEAD/han-coding - Page: https://pluginboard.ai/skills/han-coding ## Works with - ChatGPT - Claude - Gemini - GitHub Copilot - Cursor - Claude Code - Codex - Antigravity - Gemini CLI - Replit - OpenClaw - OpenCode - Hermes Agent ## Install ### ChatGPT In ChatGPT: Download the han-coding folder and zip it, then Plugins → Skills → Create → Upload from your computer. Business and Enterprise plans. View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Claude In Claude (web or desktop): Download each skill’s folder and zip it, then upload them one at a time in Customize → Skills. View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Gemini In Gemini: Download the han-coding folder, then at gemini.google.com click Customize → Skills → Create → Upload and pick the folder (or a .zip of it). View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### GitHub Copilot Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.copilot/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.copilot/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.copilot/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.copilot/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.copilot/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.copilot/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.copilot/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.copilot/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.copilot/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.copilot/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.copilot/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Cursor Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.cursor/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.cursor/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.cursor/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.cursor/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.cursor/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.cursor/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.cursor/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.cursor/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.cursor/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.cursor/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.cursor/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Claude Code In Claude Code, as a plugin: ```text /plugin marketplace add testdouble/han /plugin install han-coding@han ``` Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.claude/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.claude/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.claude/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.claude/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.claude/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.claude/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.claude/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.claude/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.claude/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.claude/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.claude/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Codex Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.agents/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.agents/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.agents/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.agents/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.agents/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.agents/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.agents/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.agents/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.agents/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.agents/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.agents/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Antigravity In Antigravity: Copy the han-coding folder into ~/.gemini/config/skills (Antigravity app and IDE) or ~/.gemini/antigravity-cli/skills (Antigravity CLI). View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Gemini CLI Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.gemini/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.gemini/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.gemini/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.gemini/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.gemini/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.gemini/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.gemini/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.gemini/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.gemini/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.gemini/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.gemini/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Replit Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis .agents/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning .agents/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview .agents/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review .agents/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough .agents/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard .agents/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api .agents/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate .agents/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning .agents/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor .agents/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd .agents/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### OpenClaw Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.openclaw/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.openclaw/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.openclaw/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.openclaw/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.openclaw/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.openclaw/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.openclaw/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.openclaw/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.openclaw/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.openclaw/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.openclaw/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### OpenCode Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.config/opencode/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.config/opencode/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.config/opencode/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.config/opencode/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.config/opencode/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.config/opencode/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.config/opencode/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.config/opencode/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.config/opencode/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.config/opencode/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.config/opencode/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding ### Hermes Agent Copy all 11 skills, in your terminal: ```shell npx -y degit testdouble/han/han-coding/skills/architectural-analysis ~/.hermes/skills/architectural-analysis npx -y degit testdouble/han/han-coding/skills/automated-test-planning ~/.hermes/skills/automated-test-planning npx -y degit testdouble/han/han-coding/skills/code-overview ~/.hermes/skills/code-overview npx -y degit testdouble/han/han-coding/skills/code-review ~/.hermes/skills/code-review npx -y degit testdouble/han/han-coding/skills/code-walkthrough ~/.hermes/skills/code-walkthrough npx -y degit testdouble/han/han-coding/skills/coding-standard ~/.hermes/skills/coding-standard npx -y degit testdouble/han/han-coding/skills/design-an-api ~/.hermes/skills/design-an-api npx -y degit testdouble/han/han-coding/skills/investigate ~/.hermes/skills/investigate npx -y degit testdouble/han/han-coding/skills/manual-test-planning ~/.hermes/skills/manual-test-planning npx -y degit testdouble/han/han-coding/skills/refactor ~/.hermes/skills/refactor npx -y degit testdouble/han/han-coding/skills/tdd ~/.hermes/skills/tdd ``` View the skills on GitHub: https://github.com/testdouble/han/tree/HEAD/han-coding --- From Pluginboard (https://pluginboard.ai).