tdd

tdd is a skill for Claude Code, Codex from Kripu77/software-factory. It costs 13 tokens per session (232 once invoked), scanned A, original, MIT.

A test-first method for implementing features and bug fixes. TDD means writing a test that fails, making it pass with the smallest change, and repeating the cycle.

In plain words
What is it for?
Use it to define test boundaries, write one behavior test at a time, implement the matching change, and repeat until the feature or fix is covered.
Why use it?
It checks intended behavior through public interfaces and helps prevent tests from depending on internal implementation details. It also keeps each coding step small and verifiable.

Skill for Claude CodeCodex

Part of the software-factory plugin — 9 skills, 9 commands shipped together

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.

agentmods
npx agentmods add skills/kripu77/software-factory/tdd
Any agent
npx skills add Kripu77/software-factory --skill tdd
Clone the repo
git clone --depth 1 https://github.com/Kripu77/software-factory

Made for: Claude Code, Codex.

Or install software-factory, the plugin that ships this one along with the rest of its 9 skills, 9 commands.

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.

agentmods badge for tdd

README.md
[![agentmods](https://agentmods.dev/badge/skills/kripu77/software-factory/tdd.svg)](https://agentmods.dev/skills/kripu77/software-factory/tdd)
Your own site
<a href="https://agentmods.dev/skills/kripu77/software-factory/tdd"><img src="https://agentmods.dev/badge/skills/kripu77/software-factory/tdd.svg" alt="Measured on agentmods" height="20"></a>
Per session 13 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 232 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00013 $0.00232
Opus 5 $0.00006 $0.00116
Sonnet 5 $0.00003 $0.00046
Haiku 4.5 $0.00001 $0.00023

Measured 4d ago against content hash 125633387f10, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 4d 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.

skills/tdd/SKILL.md · 31 lines

What it actually says

Test-Driven Development

Red then green. Consult this before and during the loop, not after.

Read CONTEXT.md if it exists so test names match the domain glossary. Respect ADRs.

Good test

Tests verify behavior through public interfaces, not internals. A good test reads like a spec and survives refactors.

Seams

A seam is the public boundary you test at. Test only at pre-agreed seams. Write the seams down before the first test. Confirm with the human if they are in the session. No test at an unconfirmed seam.

Anti-patterns

  • Implementation-coupled: mocks internals, private methods, or side channels.
  • Tautological: expected value recomputed the way the code does.
  • Horizontal slicing: all tests then all implementation. Use one test, one implementation, repeat.

Loop

  • Red before green.
  • One seam, one test, one minimal implementation per cycle.
  • Refactoring is not part of this loop. It belongs to /code-review.
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.

  1. 4d ago First seen · 31 lines · 13 tokens per session scan A 125633387f10

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository Kripu77/software-factory (7 stars, last pushed yesterday), licensed MIT. It adds 13 tokens to every session and 232 once invoked, about $0.0001 per session on Opus 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.

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