Agent skill

TDD

Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests.

Custom licenceAuto-check passedTesting & QA

Install TDD

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .claude/skills && cp -r skills-src/packages/subagents/skills/tdd .claude/skills/tdd && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .claude/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .agents/skills && cp -r skills-src/packages/subagents/skills/tdd .agents/skills/tdd && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .agents/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/packages/subagents/skills/tdd .cursor/skills/tdd && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .cursor/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/bastani-inc/atomic.git --path packages/subagents/skills/tdd

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/packages/subagents/skills/tdd .gemini/skills/tdd && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .gemini/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .github/skills && cp -r skills-src/packages/subagents/skills/tdd .github/skills/tdd && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .github/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add bastani-inc/atomic --skill tdd -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install bastani-inc/atomic tdd --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/bastani-inc/atomic.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/packages/subagents/skills/tdd .opencode/skills/tdd && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "tdd" agent skill from https://github.com/bastani-inc/atomic/tree/main/packages/subagents/skills/tdd into .opencode/skills/tdd/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "tdd", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: tdd
GitHub stars: 850
Token cost: ~1.4k tokens
SKILL.md length: 611 words
Files: 7
Skills in repo: 15
Repo updated: Oct 9, 2026
First seen: Oct 7, 2026
Licence: Custom licence

At a glance

Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests.

Works in 4 steps: Planning → Tracer Bullet → Incremental Loop → …
User wants to build features
SKILL.md covers Philosophy, Anti-Pattern: Horizontal Slices, Workflow and Auditing Existing Tests, plus 1 more section
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

TDD is an agent skill from bastani-inc/atomic. Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests. Use when user wants to build features or fix bugs using TDD, mentions "red-green-refactor", wants integration tests, asks for test-first development, or asks to review, audit, prune, or clean up low-value, duplicated, or implementation-coupled tests.

Its SKILL.md is about 1.4k tokens, which your agent loads only when the skill is triggered. The skill folder holds 6 other files (for example `deep-modules.md`, `interface-design.md` and `mocking.md`).

It sits in Testing & QA, covering Test-driven development. The repository describes itself as: The verifiable coding agent runtime. Define your coding agent's process in natural language with stages, checks, and approval gates instead of hoping it follows your…

When your agent uses it

User wants to build features
Fix bugs using TDD
Mentions red-green-refactor
Wants integration tests

Example prompts

“red-green-refactor”
“/tdd”

Workflow steps

4 steps, taken from the step headings in SKILL.md.

Planning
Tracer Bullet
Incremental Loop
Refactor

What it can do on your machine

Read from SKILL.md and the folder at commit ad79904. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

TDD loads about 1.4k tokens when it runs. Until then it costs about 89 tokens; SKILL.md has 611 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~89
When it runs · the whole SKILL.md, loaded when a task matches: ~1.4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 611 words (~1,391 tokens).

“Core principle: Tests should verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.”

— opening of SKILL.md by bastani-inc, Custom licence

name: tdd

Read the full SKILL.md on GitHub

Files

SKILL.md and 6 other files in packages/subagents/skills/tdd of bastani-inc/atomic.

SKILL.md
deep-modules.md
interface-design.md
mocking.md
refactoring.md
test-audit.md
tests.md

Open the folder on GitHubat commit ad79904

Compare with similar skills

TDD next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

TDD compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
TDD this skillbastani-inc/atomic	850	—	~1.4k	Automated safety check: Pass	Custom licence	today
TDDpietheinstrengholt/rssmonster	564	30 repos	~906	Automated safety check: Pass	MIT	yesterday
TDD WorkflowhellangleZ/burn-in-cceverywhere-ralph	112	11 repos	~2.4k	Automated safety check: Pass	None	8 mo ago
TDDsanity-io/sanity	6.4k	20 repos	~1k	Automated safety check: Pass	MIT	today
Test Driven Developmentfarm-fe/farm	5.6k	51 repos	~2.5k	Automated safety check: Pass	MIT	17 days ago
Tapd Story PipelineTencentBlueKing/bk-bcs	841	—	~2.6k	Automated safety check: Pass	Custom licence	yesterday

Similar skills

TDD
pietheinstrengholt/rssmonster
Test-driven development. An agent skill from pietheinstrengholt/rssmonster.
564 GitHub starsUsed in 30 repos~906 tokens
Testing & QAAuto-check passed
TDD Workflow
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A skill your agent uses when writing new features, fixing bugs, or refactoring code.
112 GitHub starsUsed in 11 repos~2.4k tokens
Testing & QAAuto-check passed
TDD
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Official
Test-driven development with red-green-refactor loop. An agent skill from sanity-io/sanity.
6.4k GitHub starsUsed in 20 repos~1k tokens
Testing & QAAuto-check passed
Test Driven Development
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A skill your agent uses when implementing any feature or bugfix, before writing implementation code
5.6k GitHub starsUsed in 51 repos~2.5k tokens
Testing & QAAuto-check passed
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单需求实现流水线——把一个 TAPD 需求从零推进到代码提交。自动串联技术澄清、开发计划、任务拆分、TDD 实现、架构/安全校验、代码提交六个阶段。
841 GitHub stars~2.6k tokensUpdated yesterday
Testing & QAAuto-check passed
Absolute Init
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Testing & QAAuto-check passed

Questions about TDD

What does TDD do?

Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests. TDD is an agent skill from bastani-inc/atomic. Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests.

When should I use TDD?

TDD fits situations like: user wants to build features; fix bugs using TDD; mentions red-green-refactor; wants integration tests.

How do I install TDD in Claude Code?

Run `npx skills add bastani-inc/atomic --skill tdd -a claude-code`. Or copy the skill folder (packages/subagents/skills/tdd in bastani-inc/atomic) into .claude/skills/tdd in your project. Claude Code loads it when a task matches its description.

How do I install TDD in Codex?

Run `npx skills add bastani-inc/atomic --skill tdd -a codex`. Or copy the skill folder (packages/subagents/skills/tdd in bastani-inc/atomic) into .agents/skills/tdd in your project. Codex loads it when a task matches its description.

Can I use TDD in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add bastani-inc/atomic --skill tdd -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/tdd, .gemini/skills/tdd, .github/skills/tdd and .opencode/skills/tdd in your project.

What does TDD need to run?

SKILL.md names no scripts, command-line tools or credentials: TDD is instructions for the agent only.

Does TDD access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is TDD safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does TDD use?

TDD has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.

How many tokens does TDD use?

About 1.4k tokens (SKILL.md is roughly 5.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to TDD?

Skills that share tags, products or a category with TDD: TDD (pietheinstrengholt/rssmonster, 564 stars), TDD Workflow (hellangleZ/burn-in-cceverywhere-ralph, 112 stars), TDD (sanity-io/sanity, 6.4k stars) and Test Driven Development (farm-fe/farm, 5.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains TDD?

bastani-inc (a GitHub organization) maintains it in bastani-inc/atomic, which has 850 GitHub stars. The repository holds 15 skills in this directory. The repository was last updated on October 9, 2026.

Source: bastani-inc/atomic on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

TDD

Install TDD

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Files

Compare with similar skills

Similar skills

TDD

TDD Workflow

TDD

Test Driven Development

Tapd Story Pipeline

Absolute Init

More from bastani-inc/atomic

How

Liteparse

Bun

Feedback

Prek

Tmux

Questions about TDD

Install TDD

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Files

Compare with similar skills

Similar skills

More from bastani-inc/atomic

Related

Questions about TDD