tdd SKILL.md skillA

tdd from bastani-inc/atomic is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.

Install it, pinned
mdr add bastani-inc/atomic/tdd@git:20260925.c0155b5

Pins git:20260925.c0155b5 in mdr.lock. Pin the fingerprint instead.

Audit grade
A, 17 of 17 checks passed
Kind
SKILL.md skill
Repository
bastani-inc/atomic
Path
packages/subagents/skills/tdd/SKILL.md
Versions recorded
2
Latest version
git:20260925.c0155b5, committed Sep 25, 2026
First version recorded
May 24, 2026
Size
5,586 bytes
Repository stars
880
License
a license file GitHub does not identify

Test-driven development with red-green-refactor loop, plus a value gate and audit workflow for tests. Use when user wants to build features or fix bugs using TDD, mentions "red-green-refactor", wants integration tests, asks for test-first development, or asks to review, audit, prune, or clean up low-value, duplicated, or implementation-coupled tests.

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

# Test-Driven Development

## Philosophy

**Core principle**: Tests should verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.

**Good tests** are integration-style: they exercise real code paths through public APIs. They describe _what_ the system does, not _how_ it does it. A good test reads like a specification - "user can checkout with valid cart" tells you exactly what capability exists. These tests survive refactors because they don't care about internal structure.

**Bad tests** are coupled to implementation. They mock internal collaborators, test private methods, or verify through external means (like querying a database directly instead of using the interface). The warning sign: your test breaks when you refactor, but behavior hasn't changed. If you rename an internal function and tests fail, those tests were testing implementation, not behavior.

See [tests.md](tests.md) for examples, [mocking.md](mocking.md) for mocking guidelines, and [test-audit.md](test-audit.md) for the value gate every new test must pass and the workflow for auditing existing tests.

## Anti-Pattern: Horizontal Slices
…

Read the whole file at its exact version.

How to install

The exact contents, by fingerprint
mdr add bastani-inc/atomic/tdd@sha256:5b4b54dfed264376

The line at the top of this page pins the label git:20260925.c0155b5, 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 badge

[![mdr](https://markdownregistry.com/badge/art_qpq3xxvd3b3bwtrg.svg)](https://markdownregistry.com/a/art_qpq3xxvd3b3bwtrg)

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

Versions

The registry has recorded 2 versions of this file, between May 24, 2026 and Sep 25, 2026, about one every 124 days.

versioncommittedcommitsizeaudit
git:20260925.c0155b5 latest2026-09-25 c0155b5 5,586 BA view · diff
git:20260524.d82da682026-05-24 d82da68 4,395 BA 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 (5586 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

bastani-inc/atomic · 880 stars · license a license file GitHub does not identify · pushed 2026-11-07 · branch main

API

GET https://markdownregistry.com/api/v1/artifacts/art_qpq3xxvd3b3bwtrg
GET https://markdownregistry.com/api/v1/resolve?ref=bastani-inc/atomic/tdd
GET https://markdownregistry.com/api/v1/blob/5b4b54dfed2643769f33ccf3417ddf2a5709f4283689ed18255c0150c74262c8

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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