A spec-driven development workflow that turns an idea into a specification, acceptance criteria, a plan, and then test-first implementation. TDD, or test-driven development, means writing tests before the code they check.

Use it to define a feature, record how it should be accepted, plan the work, and implement it with tests first.

It prevents implementation from starting before the expected behaviour and plan are agreed, reducing unclear requirements and rework.

sdd — Skill for Claude Code by Yeachan-Heo/oh-my-claudecode

About the project

Oh My Claude Code is a multi-agent orchestration system for Claude Code, coordinating specialized agents, commands, skills, hooks, and workflows. It is designed for developers who want Claude Code to handle coding tasks through coordinated agent roles. Catalogue entries are components of its Claude Code workflow, including agents, commands, skills, hooks, instructions, MCP configuration, and a plugin.

Yeachan-Heo/oh-my-claudecode · 40,833 stars · on GitHub · oh-my-claudecode.dev

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add Yeachan-Heo/oh-my-claudecode --skill sdd

Clone the repo

git clone --depth 1 https://github.com/Yeachan-Heo/oh-my-claudecode

Made for: Claude Code.

Or install oh-my-claudecode, the plugin that ships this one along with the rest of its 84 skills, 21 commands, 19 agents, 11 hooks, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/yeachan-heo/oh-my-claudecode/sdd/github.svg)](https://agentmods.dev/skills/yeachan-heo/oh-my-claudecode/sdd)

Your own site

<a href="https://agentmods.dev/skills/yeachan-heo/oh-my-claudecode/sdd"><img src="https://agentmods.dev/badge/skills/yeachan-heo/oh-my-claudecode/sdd/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/yeachan-heo/oh-my-claudecode/sdd"><img src="https://agentmods.dev/badge/skills/yeachan-heo/oh-my-claudecode/sdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,054 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00034	$0.01054
Opus 5.5	$0.00014	$0.00422
Sonnet 5.5	$0.00007	$0.00211
Haiku 4.5	$0.00003	$0.00105

Measured 5d ago against content hash 097875a6deaf, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

sdd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

sdd — 100% identical, 0 lines differ

skills/sdd/SKILL.md · 68 lines

How it starts

The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SDD (lite)

Interview → Spec+AC → Plan → Test-first execute. Artifacts live in spec/<slug>/ at project root (one folder per feature). No implementation code before spec/<slug>/plan.md is approved.

If args start with full: read and follow phases/spec.md, phases/criteria.md, phases/rules.md, phases/review.md, phases/tasks.md, phases/execute.md (relative to this skill's directory) in that order, confirming with the user after each artifact. Pick the slug as in Entry; every phase writes to spec/<slug>/. Then stop reading this file.

Entry

git status --short --branch; list spec/*/.
Pick the slug (kebab-case, max 40 chars, descriptive of the feature):
- On a feature branch, use the branch name without the prefix (feat/csv-export → csv-export) if spec/<that>/ exists or the task matches it.
- Otherwise derive it from the task (add CSV export of reports → csv-report-export) and show it to the user in the first message so they can correct it.
- If several spec/*/ folders exist and the task is unclear, ask which one to resume via AskUserQuestion.
Resume at the first missing artifact in spec/<slug>/ and say where you resume.
Task text comes from args or the user's message. Ask only if there is none.
Skip the flow for tasks prefixed quick:.

1. Interview (no file yet)

Read the code first; never ask what the code answers.
One question at a time via AskUserQuestion: 2-4 concrete options, a recommended pick, one-line reason why it matters.
Ask only if the answer changes behavior, scope, or a safe assumption. Otherwise decide and record it as an assumption.
Stop when an implementer would have no questions left. Typically 3-7 questions; more means the task should be split.

2. Spec → `spec/<slug>/spec.md`

One file, short:

Summary (2-3 sentences)
Decisions and assumptions (bullets, with the reason)
Out of scope
Acceptance criteria: AC-1, AC-2, ... one observable outcome each, EARS form: When <trigger>, the <system> shall <response>. / If <bad trigger>, then the <system> shall <response>. / While <state>, ...
- Bounded values: three ACs (inside, at, beyond the bound).
- Error paths: state the response and whether it is all-or-nothing.
- No implementation details, no "fast"/"correct" without a number.

Read the full file on GitHub · 68 lines

Files

What ships with it

6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

5d ago First seen · 68 lines · 34 tokens per session scan A 097875a6deaf

Subscribe to this mod's changes

sdd is a skill published in the GitHub repository Yeachan-Heo/oh-my-claudecode (40,833 stars, last pushed yesterday), licensed MIT. It adds 34 tokens to every session and 1,054 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-11-09.

Claude Code Planning TDD Testing agentic-coding ai-agents claude oh-my-opencode opencode

sdd next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
sddYeachan-Heo/oh-my-claudecode	Skill	41k	yesterday	MIT	A	34	Claude Code
moai-runmodu-ai/moai-adk	Skill	1.3k	today	Apache-2.0	A	13	Claude Code
cmux-testingmanaflow-ai/cmux	Skill	29k	today	none	A	37	Codex
spec-implementmartinffx/atelier	Skill	51	yesterday	MIT	A	63	Claude Code
code-commitmartinffx/atelier	Skill	51	yesterday	MIT	A	62	Claude Code
spec-finishmartinffx/atelier	Skill	51	yesterday	MIT	A	73	Claude Code
tdd-workflowDVNghiem/FlowDeck	Skill	42	today	MIT	A	39	Claude Code, Codex