test-driven-development

test-driven-development is a skill for Claude Code, Codex from zszz3/AgentRecall. It costs 41 tokens per session (521 once invoked), scanned B, original, MIT.

A development process called test-driven development, or TDD, in which a failing behavioral test is written before the production code. The cycle is to make the test fail, implement the smallest change, then improve the code.

In plain words
What is it for?
Use it when adding a feature, fixing a bug, refactoring code, or changing behavior, especially when a clear user-visible result can be tested.
Why use it?
It proves that the test detects the missing behavior instead of merely describing code that already exists. It also keeps changes focused on an observable requirement.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/zszz3/agentrecall/test-driven-development
Any agent
npx skills add zszz3/AgentRecall --skill test-driven-development
Clone the repo
git clone --depth 1 https://github.com/zszz3/AgentRecall

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for test-driven-development

README.md
[![agentmods](https://agentmods.dev/badge/skills/zszz3/agentrecall/test-driven-development.svg)](https://agentmods.dev/skills/zszz3/agentrecall/test-driven-development)
Your own site
<a href="https://agentmods.dev/skills/zszz3/agentrecall/test-driven-development"><img src="https://agentmods.dev/badge/skills/zszz3/agentrecall/test-driven-development.svg" alt="Measured on agentmods" height="20"></a>
Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 521 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00041 $0.00521
Opus 5 $0.00020 $0.00260
Sonnet 5 $0.00008 $0.00104
Haiku 4.5 $0.00004 $0.00052

Measured 4d ago against content hash 474ae635a062, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

test-driven-development scanned grade B with 1 finding 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 4d 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.

Strips warnings and disclaimersmediumAnti-refusal

Omitting safety caveats hides risk from the user and is a common jailbreak preamble.

- Focused tests and relevant regressions pass without warnings.
apps/main-2.0/assets/bundled-skills/test-driven-development/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test-Driven Development

Core rule

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Tests written after implementation describe what was built. Tests written first define what should be built and prove that the test can catch its absence.

Red, green, refactor

1. Red

Write one small test for one observable behavior.

  • Use a name that states the expected result.
  • Exercise real code. Mock only boundaries that cannot be used safely or deterministically.
  • Prefer public behavior over private methods, internal call counts, CSS details, or implementation structure.
  • Use temporary homes, prefixes, databases, and synthetic fixtures for filesystem or installation behavior.

Run only the new test. Confirm that it fails because the requested behavior is missing. A syntax error, invalid fixture, missing dependency, or unrelated crash is not a valid red state.

If the test passes immediately, it does not demonstrate the new requirement. Correct the test before writing production code.

2. Green

Write the smallest implementation that satisfies the failing behavior.

  • Change one cause at a time.
  • Do not add speculative options or unrelated cleanup.
  • Do not weaken the assertion to fit the implementation.

Run the new test again and confirm it passes. Then run the nearest relevant test set to catch regressions.

3. Refactor

Only after green:

  • Remove duplication.
  • Improve names and boundaries.
  • Simplify control flow.
  • Keep behavior unchanged and rerun the tests.

Repeat the cycle for the next behavior.

Bug fixes

Reproduce the original symptom in a test before changing the fix site. The test must fail for the observed reason and pass after the root cause is fixed. When practical, temporarily revert the fix once to confirm the regression test turns red again.

Exceptions

Generated files and data-only metadata do not need artificial unit tests, but the code that loads or validates them does. Throwaway exploration must be discarded before production work begins. Ask the user before intentionally skipping test-first implementation.

Read the full file on GitHub · 69 lines

Changes

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.

  1. 4d ago First seen · 69 lines · 41 tokens per session scan B 474ae635a062

Subscribe to this mod's changes

test-driven-development is a skill published in the GitHub repository zszz3/AgentRecall (762 stars, last pushed today), licensed MIT. It adds 41 tokens to every session and 521 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it B with 1 finding (strips warnings and disclaimers). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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