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 skills add vignesh2027/AI-AGENT-SKILLS --skill test-driven-developmentgit clone --depth 1 https://github.com/vignesh2027/AI-AGENT-SKILLSWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/vignesh2027/ai-agent-skills/test-driven-development)<a href="https://agentmods.dev/skills/vignesh2027/ai-agent-skills/test-driven-development"><img src="https://agentmods.dev/badge/skills/vignesh2027/ai-agent-skills/test-driven-development.svg" alt="Measured on agentmods" height="20"></a>What 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 5.1 | $0.00014 | $0.00697 |
| Opus 5 | $0.00007 | $0.00349 |
| Sonnet 5 | $0.00003 | $0.00139 |
| Haiku 4.5 | $0.00001 | $0.00070 |
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 6d 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.
How it starts
The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Overview
TDD is not about testing — it's about design. Writing tests first forces you to define the interface before the implementation, catches over-engineering, and creates a living specification. The test suite is proof of correctness, not evidence of effort.
When to Use
- Before implementing any function, class, or service with business logic
- When fixing a bug (write a test that reproduces it first)
- When the implementation will be difficult to test after the fact
Process
Step 1: Write a failing test (Red)
Write the simplest test that captures one behavior. Run it. It must fail. If it passes without implementation, the test is wrong.
Step 2: Write the minimum implementation (Green)
Write the least code that makes the test pass. Do not add functionality that isn't tested yet. Resist the urge to generalize.
Step 3: Refactor (Refactor)
Now that the test passes, clean the implementation. Extract duplication, improve names, simplify logic. Run tests after each change.
Step 4: Repeat for the next behavior
Add one behavior at a time. The test suite grows incrementally.
Step 5: Write edge case tests
After the happy path works: test empty inputs, boundary values, error conditions, concurrent access, and failure modes.
Step 6: Test the contract, not the implementation
Tests should describe what the function does, not how it does it. Avoid testing internal state — test inputs and outputs.
Step 7: Keep tests fast and independent
Each test must run in isolation. No shared mutable state between tests. Tests that require a specific order are fragile.
Step 8: Maintain the test suite
A test that is wrong is worse than no test. Delete tests that no longer represent the system. Update tests when behavior intentionally changes.
Anti-Rationalizations
"I'll add tests after I'm done implementing" Tests written after implementation test what the code does. Tests written before implementation test what the code should do. These are different.
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.
- 6d ago First seen · 74 lines · 14 tokens per session scan A 6e565c1f1ecd
test-driven-development is a skill published in the GitHub repository vignesh2027/AI-AGENT-SKILLS (2 stars, last pushed 8d ago), licensed MIT. It adds 14 tokens to every session and 697 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
Other skills, from other repositories
tdd
A test-driven development workflow based on repeating three stages: write a failing test, make it pass, then improve the code. The tests focus on what users can do through public interfaces rather than internal implementation details.
tdd
Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration tests.
tdd
Test-driven development — write the failing test first, then the code. Triggers on TDD, test first, write tests, test-driven.
test-driven-development
Write a failing test first, watch it fail, then write the minimal code to pass.
test-driven-development
Use when implementing any feature or bugfix, before writing implementation code.
kotlin-testing
Kotlin testing patterns with Kotest, MockK, coroutine testing, property-based testing, and Kover coverage. Follows TDD methodology with idiomatic Kotlin practices.