test-driven-development

A development workflow based on test-driven development (TDD), where you write a failing behavior test, implement the smallest fix, and then clean up the code while tests pass.

In plain words
What is it for?
Use it for features, bug fixes, and behavior changes, including a focused edge or error case, while preserving existing tests for safe refactoring.
Why use it?
It makes the required behavior explicit before implementation and provides a recorded check that the change works.

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/drizzy07x/skillquiver/test-driven-development
Any agent
npx skills add Drizzy07x/Skillquiver --skill test-driven-development
Clone the repo
git clone --depth 1 https://github.com/Drizzy07x/Skillquiver

Made for: Claude Code, Codex.

Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 676 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. 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 $0.00026 $0.00676
Opus 5 $0.00013 $0.00338
Sonnet 5 $0.00005 $0.00135
Haiku 4.5 $0.00003 $0.00068

Measured 2d ago against content hash c35df5f6be28, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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.

skills/test-driven-development/SKILL.md · 86 lines

How it starts

The opening of the file, as written. The whole thing — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test-Driven Development

Write one behavioral test, observe the expected failure, write the minimum code to pass, and refactor only while green.

Scope

Use TDD for features, bug fixes, and externally observable behavior changes. For a pure behavior-preserving refactor, preserve existing green tests and add coverage only for an uncovered contract the refactor could break. Ask before skipping TDD for throwaway prototypes, generated code, or configuration-only changes.

Production code written before its failing test is not a red-green cycle. Do not keep it as a reference: revert that implementation, establish red, and implement from the test.

Cycle

1. Red

Write the smallest test that expresses one required behavior through the highest practical public seam.

  • Name the behavior precisely.
  • Exercise real production code; mock only an external boundary that cannot be used safely or deterministically.
  • Cover the requested example first, then one meaningful edge or error case.
  • Run only the focused test while iterating.

Record the command, non-zero exit, and decisive assertion output. Confirm that the test failed because the behavior is missing, not because of syntax, setup, imports, or the wrong command. A passing test or a test that errors does not establish red; correct it and rerun.

2. Green

Implement only enough production behavior to satisfy the red test. Do not add options, abstractions, validation, or adjacent cleanup that no current test or requirement demands.

Rerun the identical focused command. Fix production code rather than weakening the assertion. Record the zero exit and passing output. If existing focused tests now fail, resolve the regression before continuing.

3. Refactor

Only after green, remove duplication, improve names, or simplify structure without adding behavior. Keep the focused tests green after every structural change. If the next requirement needs new behavior, start another red cycle.

Test integrity

Before writing or changing a non-trivial test, read writing-good-tests.md. In particular:

Read the full file on GitHub · 86 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 2d ago First seen · 86 lines · 26 tokens per session scan A c35df5f6be28

Subscribe to this mod's changes

test-driven-development is a skill published in the GitHub repository Drizzy07x/Skillquiver (2 stars, last pushed 10d ago), licensed MIT. It adds 26 tokens to every session and 676 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.

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