test-driven-development

A development method called test-driven development, or TDD, where you write a test for a missing behaviour, see it fail, then add the smallest code that makes it pass.

In plain words
What is it for?
Use it when adding or changing behaviour: write one failing test, implement the minimum fix, run the full suite, and then improve the code while tests remain passing.
Why use it?
It confirms that a test actually checks new behaviour and helps limit changes to what is required.

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/new1direction/korgex/test-driven-development
Any agent
npx skills add New1Direction/korgex --skill test-driven-development
Clone the repo
git clone --depth 1 https://github.com/New1Direction/korgex

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 287 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 $0.00021 $0.00287
Opus 5 $0.00010 $0.00143
Sonnet 5 $0.00004 $0.00057
Haiku 4.5 $0.00002 $0.00029

Measured 2d ago against content hash f7e5872e1d27, 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.

src/skills_builtin/test-driven-development/SKILL.md · 27 lines

What it actually says

Use this whenever you add or change behaviour. The discipline is what makes the test trustworthy — a test you never saw fail proves nothing.

  1. RED — write one failing test. Pick the smallest next behaviour. Write a test that asserts it, using real code (no mocks unless a dependency is truly unavailable). One behaviour per test; name it for the behaviour.
  2. Watch it fail. Run it. Confirm it fails for the right reason (the feature is missing), not a typo or import error. If it passes already, you're testing existing behaviour — fix the test.
  3. GREEN — minimal code. Write the least code that makes it pass. Don't add options, abstractions, or features the test doesn't demand.
  4. Watch it pass. Run it; confirm the whole suite stays green and the output is clean (no new warnings).
  5. REFACTOR. Improve names and remove duplication while green. Don't add behaviour here.
  6. Repeat for the next behaviour.

If a test is hard to write, the design is usually too coupled — simplify the interface before continuing.

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 · 27 lines · 21 tokens per session scan A f7e5872e1d27

Subscribe to this mod's changes

test-driven-development is a skill published in the GitHub repository New1Direction/korgex (5 stars, last pushed 2mo ago), licensed MIT. It adds 21 tokens to every session and 287 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.