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.
npx agentmods add skills/mamahoos/dot-files/test-driven-developmentnpx skills add mamahoos/dot-files --skill test-driven-developmentgit clone --depth 1 https://github.com/mamahoos/dot-filesWhat 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 | $0.00050 | $0.03729 |
| Opus 5 | $0.00025 | $0.01865 |
| Sonnet 5 | $0.00010 | $0.00746 |
| Haiku 4.5 | $0.00005 | $0.00373 |
Grade A, and why
test-driven-development 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 2d 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.
This is a copy
98% identical to test-driven-development — 1 line differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 400 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
Overview
Write a failing test before writing the code that makes it pass. For bug fixes, reproduce the bug with a test before attempting a fix. Tests are proof — "seems right" is not done. A codebase with good tests is an AI agent's superpower; a codebase without tests is a liability.
When to Use
- Implementing any new logic or behavior
- Fixing any bug (the Prove-It Pattern)
- Modifying existing functionality
- Adding edge case handling
- Any change that could break existing behavior
When NOT to use: Pure configuration changes, documentation updates, or static content changes that have no behavioral impact.
Related: For browser-based changes, combine TDD with runtime verification using Chrome DevTools MCP — see the Browser Testing section below.
Discover the Stack First
The TDD cycle is universal; the commands are not. Before writing the first test, discover how this repository tests, and use its commands for every RED, GREEN, and verification step:
- Language and build system —
package.json,pom.xml/build.gradle,pyproject.toml,go.mod,Cargo.toml,Gemfile, aMakefile - Checked-in wrappers — prefer
./gradlew,./mvnw,make test, or a repo script over globally installed tools - Test framework and configuration — and how it runs a single focused test vs the full suite
- Existing conventions — where tests live, how files are named, what patterns neighboring tests follow
- Documented commands — README, CONTRIBUTING, and CI workflows show the commands that actually gate merges
Run the repository's focused-test command during the loop and its full-suite command before completion. Never assume a default like npm test — a Gradle, Cargo, or pytest project has its own equivalent.
The examples below use TypeScript for illustration; the workflow is identical in any language once you've discovered the project's own tooling.
The TDD Cycle
RED GREEN REFACTOR
Write a test Write minimal code Clean up the
that fails ──→ to make it pass ──→ implementation ──→ (repeat)
│ │ │
▼ ▼ ▼
Test FAILS Test PASSES Tests still PASS
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.
- 2d ago First seen · 400 lines · 50 tokens per session scan A a65ec1f2cc60
test-driven-development is a skill published in the GitHub repository mamahoos/dot-files (3 stars, last pushed 3d ago), licensed MIT. It adds 50 tokens to every session and 3,729 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 98% identical to test-driven-development, differing in 1 line, and is treated as a copy.
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