A test-first software-development method in which you write a failing test, make it pass, and then improve the code; this cycle is called red-green-refactor.

It is for building features or fixing bugs with tests first, including integration tests that check how parts of a system work together.

It helps catch regressions early and encourages code changes that are checked by automated tests.

How mythopoeic/mcp-server-demo configures Claude Code and Codex

Reuse

Borrowing it

Nothing to install: this file belongs to mythopoeic/mcp-server-demo. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/mythopoeic/mcp-server-demo/main/.agents/skills/tdd/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/mythopoeic/mcp-server-demo

Made for: Claude Code, Codex.

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/mythopoeic/mcp-server-demo/tdd/github.svg)](https://agentmods.dev/skills/mythopoeic/mcp-server-demo/tdd)

Your own site

<a href="https://agentmods.dev/skills/mythopoeic/mcp-server-demo/tdd"><img src="https://agentmods.dev/badge/skills/mythopoeic/mcp-server-demo/tdd/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/mythopoeic/mcp-server-demo/tdd"><img src="https://agentmods.dev/badge/skills/mythopoeic/mcp-server-demo/tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 958 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 unknown 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	$0.00033	$0.00958
Opus 5.5	$0.00013	$0.00383
Sonnet 5.5	$0.00007	$0.00192
Haiku 4.5	$0.00003	$0.00096

Measured 2mo ago against content hash 13722957277e, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

tdd 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 2mo 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.

.agents/skills/tdd/SKILL.md · 109 lines

The source is not reproduced here

No licence file

Read it on GitHub

Files

What ships with it

3 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.

2mo ago First seen · 109 lines · 33 tokens per session scan A 13722957277e

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository mythopoeic/mcp-server-demo (0 stars, last pushed 4mo ago), with no licence file. It adds 33 tokens to every session and 958 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 2026-08-31.

TDD Testing

tdd next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
tddmythopoeic/mcp-server-demo	Skill	0	4mo ago	none	A	33	Claude Code, Codex
engram-testing-coverageGentleman-Programming/engram	Skill	7.8k	yesterday	MIT	A	25	Claude Code, Codex
principle-test-behavior-not-implementationmichael-denyer/pstack-claude	Skill	4.1k	yesterday	MIT	A	50	Claude Code
tddcodewithmukesh/dotnet-claude-kit	Skill	805	2d ago	MIT	A	81	Claude Code
nw-ddd-eventsourcingnWave-ai/nWave	Skill	631	yesterday	MIT	A	38	Claude Code
nw-fp-clojurenWave-ai/nWave	Skill	631	yesterday	MIT	A	25	Claude Code
nw-leanux-methodologynWave-ai/nWave	Skill	631	yesterday	MIT	A	37	Claude Code

mcp-server-demo: Skill for Claude Code