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tdd

tdd is a skill for Claude Code, Codex from PyModel/react-frontend-skills. It costs 12 tokens per session (1,191 once invoked), scanned A, a copy of tdd, MIT.

A guide to Test-Driven Development (TDD), a method where you write a failing test, make it pass with minimal code, then clean up the code.

In plain words
What is it for?
Use it when writing tests first, following the red-green-refactor cycle, designing test data, or reviewing and improving test suites.
Why use it?
It gives coding agents a repeatable way to design tests and implement changes without losing the intended behavior.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

not rated 37repo +2 changed 20d ago A scan 12 tokens copy · 98% MIT

Good fit Use it when writing tests first, following the red-green-refactor cycle, designing test data, or reviewing and improving test suites.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/pymodel/react-frontend-skills/tdd
View source ↗ PyModel/react-frontend-skills npmjs.com
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 PyModel/react-frontend-skills --skill tdd
Clone the repo
git clone --depth 1 https://github.com/PyModel/react-frontend-skills

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.

agentmods badge for tdd

README.md
[![agentmods](https://agentmods.dev/badge/skills/pymodel/react-frontend-skills/tdd/github.svg)](https://agentmods.dev/skills/pymodel/react-frontend-skills/tdd)
Your own site
<a href="https://agentmods.dev/skills/pymodel/react-frontend-skills/tdd"><img src="https://agentmods.dev/badge/skills/pymodel/react-frontend-skills/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.

agentmods 80×15 button for tdd

Your own site · 80×15
<a href="https://agentmods.dev/skills/pymodel/react-frontend-skills/tdd"><img src="https://agentmods.dev/badge/skills/pymodel/react-frontend-skills/tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 12 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,191 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 98% copy Near-identical to another mod 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 5.1 $0.00012 $0.01191
Opus 5.5 $0.00005 $0.00476
Sonnet 5.5 $0.00002 $0.00238
Haiku 4.5 $0.00001 $0.00119

Measured 20d ago against content hash 3c73134c523e, 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 20d 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

This is a copy

98% identical to tdd — 15 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/tdd/SKILL.md · 115 lines

How it starts

The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Community Test-Driven Development Best Practices

Comprehensive guide to Test-Driven Development practices, designed for AI agents and LLMs. Contains 42 rules across 8 categories, prioritized by impact to guide test writing, refactoring, and code generation.

When to Apply

Reference these guidelines when:

  • Writing new tests using TDD workflow
  • Implementing the red-green-refactor cycle
  • Designing test structure and organization
  • Creating test data and fixtures
  • Reviewing or refactoring existing test suites

TDD Workflow

  1. RED: Write a failing test that defines desired behavior
  2. GREEN: Write minimal code to make the test pass
  3. REFACTOR: Clean up code while keeping tests green
  4. Repeat for each new behavior

Rule Categories by Priority

Priority Category Impact Prefix
1 Red-Green-Refactor Cycle CRITICAL cycle-
2 Test Design Principles CRITICAL design-
3 Test Isolation & Dependencies HIGH isolate-
4 Test Data Management HIGH data-
5 Assertions & Verification MEDIUM assert-
6 Test Organization & Structure MEDIUM org-
7 Test Performance & Reliability MEDIUM perf-
8 Test Pyramid & Strategy LOW strat-

Quick Reference

1. Red-Green-Refactor Cycle (CRITICAL)

  • cycle-write-test-first - Write the Test Before the Implementation
  • cycle-minimal-code-to-pass - Write Only Enough Code to Pass the Test
  • cycle-refactor-after-green - Refactor Immediately After Green
  • cycle-verify-test-fails-first - Verify the Test Fails Before Writing Code
  • cycle-small-increments - Take Small Incremental Steps
  • cycle-maintain-test-list - Maintain a Test List

2. Test Design Principles (CRITICAL)

  • design-test-behavior-not-implementation - Test Behavior Not Implementation
  • design-one-assertion-per-test - One Logical Assertion Per Test
  • design-descriptive-test-names - Use Descriptive Test Names
  • design-aaa-pattern - Follow the Arrange-Act-Assert Pattern
  • design-test-edge-cases - Test Edge Cases and Boundaries
  • design-avoid-logic-in-tests - Avoid Logic in Tests

Read the full file on GitHub · 115 lines

Files

What ships with it

42 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.

  1. 20d ago Changed · -8 lines · -84 tokens per session 3c73134c523e
  2. 1mo ago First seen · 123 lines · 96 tokens per session scan A 342067a0d37a

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository PyModel/react-frontend-skills (37 stars, last pushed 3d ago), licensed MIT. It adds 12 tokens to every session and 1,191 once invoked, about $0.0000 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 98% identical to tdd, differing in 15 lines, and is treated as a copy.

Claude CodeTDDTestingagent-skillsai-agentsai-coding-assistantcodexcursor
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