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writing-tests SKILL.md skillA

writing-tests from dayfinggg/openai-codex-agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

Install it, pinned

mdr add dayfinggg/openai-codex-agent-skills/writing-tests@git:20261015.18f69f5

Pins git:20261015.18f69f5 in mdr.lock. Pin the fingerprint instead.

Audit grade: A, 17 of 17 checks passed
Kind: SKILL.md skill
Repository: dayfinggg/openai-codex-agent-skills
Path: codex/skills/writing-tests/SKILL.md
Versions recorded: 1
Latest version: git:20261015.18f69f5, committed Oct 15, 2026
Size: 5,680 bytes
Repository stars: 8
License: MIT

Writes and reviews automated tests test-first, in each language's test framework. Use when writing, changing, or reviewing tests, fixing a bug in a project with tests, or adding behavior that tests should cover.

Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.

What the file says

# Writing tests

Tests are what make code safe to change. Martin's rule is that test code is as important as production code, so it gets the same care for names, structure, and simplicity. Code-level rules live in the writing-clean-code skill.

## Test-driven development

Use the test-first cycle for new logic and for bug fixes when the project has a test suite, unless the user asks for a different workflow.

1. **Red.** Write the smallest test that fails for the next piece of behavior. A compile error counts as failing.
2. **Green.** Write only enough production code to make that test pass.
3. **Refactor.** Clean up production and test code while all tests stay green.

Work in small steps and run the tests after each one. As the tests get more specific, the code gets more generic, so never answer a new test with an `if` for that exact input. If the code only passes by special-casing test data, the design is wrong.

For a bug fix, first write a test that reproduces the bug and watch it fail for the right reason, then fix the code.

## What makes a test clean
…

Read the whole file at its exact version.

How to install

The exact contents, by fingerprint

mdr add dayfinggg/openai-codex-agent-skills/writing-tests@sha256:98132e086a53d187

The line at the top of this page pins the label git:20261015.18f69f5, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.

Badge

[![mdr](https://markdownregistry.com/badge/art_crukkzl4d2t3g7ux.svg)](https://markdownregistry.com/a/art_crukkzl4d2t3g7ux)

1 badge image fetches in 30 days. What the badge shows.

Versions

The registry has recorded 1 version of this file, committed on Oct 15, 2026.

version	committed	commit	size	audit
git:20261015.18f69f5 latest	2026-10-15	18f69f5	5,680 B	A	view

Audit of the latest version

A 17 of 17 checks passed. Fixed automatic checks with no AI involved, so the same checks give the same answer every run.

pass: Frontmatter block present
pass: Frontmatter declares a name
pass: Frontmatter declares a description
pass: Size between 200 bytes and 200 KB (5680 bytes)
pass: No zero-width or bidi control characters
pass: No instruction hidden inside an HTML comment
pass: No link to an exfiltration or paste host
pass: No credential-shaped string
pass: No instruction to send local credentials anywhere
pass: No text hidden with inline styles
pass: No prompt-injection phrasing
pass: No curl or wget piped into a shell
pass: No recursive delete of root, home or parent
pass: No instruction to read or print local credentials
pass: No base64 blob over 200 characters
pass: No link to a raw IP address
pass: No script tag

Source

GitHub

dayfinggg/openai-codex-agent-skills · 8 stars · license MIT · pushed 2026-10-15 · branch main

API

GET https://markdownregistry.com/api/v1/artifacts/art_crukkzl4d2t3g7ux
GET https://markdownregistry.com/api/v1/resolve?ref=dayfinggg/openai-codex-agent-skills/writing-tests
GET https://markdownregistry.com/api/v1/blob/98132e086a53d187dc6f359500c5aab51ca261aa5437597c231a09e65e09a4df

Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.

Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.

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