Drives implementation by writing a failing test first, then the smallest code that passes it. Use this before writing implementation code for any feature or bugfix, when a bug needs a regression test, when existing code is hard to change safely, or when someone asks whether a change is covered. Also use to decide what is worth testing and what is not.
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
## The loop
1. **Red** — write one test that fails for the right reason. Run it. A test that passes immediately
is testing nothing; a test that errors instead of failing is testing the wrong thing.
2. **Green** — the smallest change that makes it pass. Ugly is fine here.
3. **Refactor** — clean up with the test green. If it goes red, you changed behavior, not structure.
Never skip step 1. Writing the test after the code produces a test shaped to the implementation,
which is the one shape that cannot catch the implementation being wrong.
## What to test
Test behavior at the boundary a caller actually depends on. For each unit ask: if this broke
silently, who notices and how? If the answer is nobody, delete the code rather than test it.
- **Test**: branching logic, boundary conditions, error paths, anything with a past bug, contracts
between modules.
- **Do not test**: getters, framework behavior, private helpers reachable only through a public path
already covered, exact wording of log lines.
## Bugs
Every bug gets a failing test *before* the fix, reproducing it at the smallest scope that shows it.
…
The line at the top of this page pins the label git:20260901.aa45383, 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.
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 (2696 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
cbrock84/headcount · 2,076 stars · license MIT · pushed 2026-10-18 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_4lt5yvl33h4li7iu
GET https://markdownregistry.com/api/v1/resolve?ref=cbrock84/headcount/test-driven-development
GET https://markdownregistry.com/api/v1/blob/11c5bb96274ff6daa521ca25ce87ef1fe1e046a83a6865f1dac37a9ca58c8b62
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.
cbrock84/headcount · plugins/corporate-strategy/skills/chief-strategy-officer/SKILL.md · Owns where the business plays and how it wins over a multi-year horizon — portfolio choices, corporate development…
cbrock84/headcount · plugins/corporate-strategy/skills/market-entry/SKILL.md · Decides whether and how to enter a new market — sizing demand from the bottom up rather than from a market report…
cbrock84/headcount · plugins/corporate-strategy/skills/portfolio-strategy/SKILL.md · Decides where capital and attention go across business lines, products, and markets — what to fund, hold, harvest, or…
cbrock84/headcount · plugins/corporate-strategy/skills/scenario-planning/SKILL.md · Plans under genuine uncertainty — building scenarios, identifying which assumptions are load-bearing, setting…
cbrock84/headcount · plugins/corporate-strategy/skills/strategic-alliances/SKILL.md · Structures partnerships that change what the business can do — technology integrations, channel and reseller…
cbrock84/headcount · plugins/customer-experience/skills/chief-customer-officer/SKILL.md · Owns the customer's experience after the sale — support, success, escalation, and the feedback loop back into product…
cbrock84/headcount · plugins/customer-experience/skills/customer-onboarding-and-implementation/SKILL.md · Takes a new customer from signature to working — setting a definition of live that both sides agreed before the…
cbrock84/headcount · plugins/customer-experience/skills/customer-success-management/SKILL.md · Runs the ongoing relationship with accounts after the sale — segmenting coverage against account value, building a…
cbrock84/headcount · plugins/customer-experience/skills/escalation-management/SKILL.md · Handles customer situations that have exceeded normal support — severity assessment, incident communication, executive…
cbrock84/headcount · plugins/customer-experience/skills/self-service-and-knowledge/SKILL.md · Builds the help center, in-product guidance, and knowledge base that let customers resolve problems without contacting…
addyosmani/agent-skills · skills/test-driven-development/SKILL.md · Drives development with tests using the red-green-refactor loop. Use when implementing any logic, fixing any bug, or…
mvschwarz/openrig · skills/_canonical/process/test-driven-development/SKILL.md · Use when implementing any feature or bugfix, before writing implementation code
mvschwarz/openrig · packages/daemon/specs/agents/shared/skills/process/test-driven-development/SKILL.md · Use when implementing any feature or bugfix, before writing implementation code
a5c-ai/babysitter · library/methodologies/superpowers/skills/test-driven-development/SKILL.md · Use when implementing any feature or bugfix, before writing implementation code. Enforces RED-GREEN-REFACTOR cycle.
a5c-ai/babysitter · library/methodologies/rpikit/skills/test-driven-development/SKILL.md · Test-first development practice where test specifications are written before production code, integrated into plan…
a5c-ai/babysitter · library/methodologies/cc10x/skills/test-driven-development/SKILL.md · Strict RED-GREEN-REFACTOR cycle enforcement. Tests are never skipped or deferred. Run mode only, never watch mode. Exit…
