A test-driven development workflow: write a failing test first, make it pass with the smallest implementation, then improve the code while keeping the tests passing.

Use it to create tests for normal, error, and boundary cases, implement features from those tests, refactor safely, and check that coverage reaches the stated target.

It turns expected behaviour into checks before implementation, helping catch regressions and clarify edge cases during feature work, bug fixes, and refactoring. TDD means test-driven development.

tdd — Skill for Claude Code and Codex by Luohaothu/everything-codex

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 Luohaothu/everything-codex --skill tdd

Clone the repo

git clone --depth 1 https://github.com/Luohaothu/everything-codex

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/luohaothu/everything-codex/tdd/github.svg)](https://agentmods.dev/skills/luohaothu/everything-codex/tdd)

Your own site

<a href="https://agentmods.dev/skills/luohaothu/everything-codex/tdd"><img src="https://agentmods.dev/badge/skills/luohaothu/everything-codex/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/luohaothu/everything-codex/tdd"><img src="https://agentmods.dev/badge/skills/luohaothu/everything-codex/tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 44 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 787 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. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

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	$0.00044	$0.00787
Opus 5.5	$0.00018	$0.00315
Sonnet 5.5	$0.00009	$0.00157
Haiku 4.5	$0.00004	$0.00079

Measured 1mo ago against content hash 54c7579b23c9, 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 1mo 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 · 118 lines

How it starts

The opening of the file, as written. The whole thing — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.

TDD Guide Mode

BEHAVIORAL CONSTRAINTS:

ALWAYS write tests BEFORE implementation code
Follow RED -> GREEN -> REFACTOR cycle strictly
Target 80%+ code coverage
Each test should verify a single behavior

Your Role

You are a TDD specialist ensuring all development follows test-first methodology.

TDD Workflow

Step 1: Define Interfaces (SCAFFOLD)

Define types/interfaces for inputs and outputs before writing any code.

Step 2: Write Failing Tests (RED)

Write comprehensive tests covering:

Happy path scenarios
Edge cases (null, empty, boundary values)
Error scenarios
Integration points

Step 3: Run Tests (Verify FAIL)

Tests should FAIL -- we haven't implemented yet. Verify they fail for the right reason.

Step 4: Write Minimal Implementation (GREEN)

Write the minimum code needed to make tests pass. No more, no less.

Step 5: Run Tests (Verify PASS)

All tests should now PASS.

Step 6: Refactor (IMPROVE)

Improve code quality while keeping tests green:

Remove duplication
Improve naming
Optimize performance
Extract constants

Step 7: Verify Coverage

Ensure 80%+ coverage achieved. Add more tests if below threshold.

TDD Cycle

RED -> GREEN -> REFACTOR -> REPEAT

RED:      Write a failing test
GREEN:    Write minimal code to pass
REFACTOR: Improve code, keep tests passing
REPEAT:   Next feature/scenario

Coverage Requirements

Minimum 80% coverage (unit + integration)
100% required for financial calculations, auth logic, security-critical code
All edge cases covered
Error scenarios tested
Boundary conditions verified

Test Types

Unit Tests (Mandatory)

Individual functions and utilities
Component logic
Pure functions

Integration Tests (Mandatory)

API endpoints
Database operations
Service interactions

E2E Tests (For Critical Flows)

Critical user flows
Complete workflows
Use /e2e skill for Playwright tests

Mocking External Dependencies

Mock databases, APIs, and services to isolate unit tests. Use real dependencies for integration tests when possible.

Read the full file on GitHub · 118 lines

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.

1mo ago First seen · 118 lines · 44 tokens per session scan A 54c7579b23c9

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository Luohaothu/everything-codex (25 stars, last pushed 2mo ago), licensed MIT. It adds 44 tokens to every session and 787 once invoked, about $0.0002 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 2026-09-03.

TDD Testing

engram-testing-coverage

TDD and coverage standards for Engram. Trigger: When implementing behavior changes in any package.

Gentleman-Programming/engram · 25 tokens

conductor-implement

Execute tasks from a track's implementation plan following TDD workflow.

rmyndharis/antigravity-skills · 17 tokens

principle-test-behavior-not-implementation

Apply when you write, change, or keep a test. Assert what the code's users can observe, so that the test fails when that behavior breaks and keeps passing when only the internals change.

michael-denyer/pstack-claude · 50 tokens

iterative-development

TDD iteration loops using Claude Code Stop hooks - runs tests after each response, feeds failures back automatically.

alinaqi/maggy · 24 tokens

python

Python development with ruff, mypy, pytest - TDD and type safety.

alinaqi/maggy · 18 tokens

tdd

This skill should be used when the user wants to implement features or fix bugs using test-driven development. Enforces the RED-GREEN-REFACTOR cycle with vertical slicing, context isolation between test writing and implementation, human checkpoints, and auto-test feedback loops. Uses multi-agent orchestration with the…

glebis/claude-skills · 92 tokens