Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration 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
TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle: consult them before and during the loop, not after.
When exploring the codebase, read `CONTEXT.md` (if it exists) so test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
## What a good test is
Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification: "user can checkout with valid cart" tells you exactly what capability exists, and it survives refactors because it doesn't care about internal structure.
See [tests.md](tests.md) for examples and [mocking.md](mocking.md) for mocking guidelines.
## Seams: where tests go
A **seam** is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.
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The line at the top of this page pins the label git:20260924.44e305d, 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.
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Source
GitHub
dcouple/pane · 603 stars · license a license file GitHub does not identify · pushed 2026-11-07 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_uvvxijekzivacdlv
GET https://markdownregistry.com/api/v1/resolve?ref=dcouple/pane/tdd
GET https://markdownregistry.com/api/v1/blob/684438cdcaee304d45ff8a9ed67880bb7705af4388ee676f4fbf187f89ff35fd
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dcouple/pane · main/src/services/paneChatBundle/skills/babysit-pr/SKILL.md · Use after a pull request is open to watch its CI and review-bot comments until it is ready. Fixes real findings…
dcouple/pane · main/src/services/paneChatBundle/skills/brief/SKILL.md · Use when a problem, idea, or change of intent is worth capturing as a long-form page, or the person asks to write it…
dcouple/pane · main/src/services/paneChatBundle/skills/bug-intake/SKILL.md · Use when the person reports broken behaviour or starts a session to file a bug. Reproduces and reports. Never fixes.
dcouple/pane · main/src/services/paneChatBundle/skills/codebase-design/SKILL.md · Shared vocabulary for designing deep modules. Use when the user wants to design or improve a module's interface, find…
dcouple/pane · main/src/services/paneChatBundle/skills/cold-read/SKILL.md · Give a fresh agent something to walk through with zero context - a PR body, a landing page, a document, a process…
dcouple/pane · main/src/services/paneChatBundle/skills/create-ticket/SKILL.md · Capture work and evolving intent during discussion as one or more GitHub tickets, published briefs, or both. Use for…
dcouple/pane · main/src/services/paneChatBundle/skills/discussion/SKILL.md · Have an interactive discussion about a topic, approach, feature, or bug without making code changes. Researches the…
dcouple/pane · main/src/services/paneChatBundle/skills/eli5/SKILL.md · Teach an unfamiliar topic from first principles with a picture-first HTML explanation, published to the workspace's…
dcouple/pane · main/src/services/paneChatBundle/skills/excalidraw-pr-diagrams/SKILL.md · Draw Excalidraw diagrams that make a visual argument, such as a pull request's before/after visual overview, an…
cursor/plugins · pstack/skills/tdd/SKILL.md · Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious…
cursor/plugins · harness/pstack/claude-code/skills/tdd/SKILL.md · Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious…
nightly-labs/openbot · marketplace/production-catalog/bundles/pstack/skills/tdd/SKILL.md · Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious…
michael-denyer/pstack-claude · plugins/pstack/skills/tdd/SKILL.md · Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious…
backnotprop/pstack · skills/tdd/SKILL.md · Use only when the user explicitly asks for TDD, a failing test, or a regression test, OR when the bug has an obvious…
