tdd

tdd is a skill for Claude Code from bharat3645/The-Ideal-Harness. It costs 62 tokens per session (468 once invoked), scanned A, original, MIT.

A coding method called test-driven development, or TDD, that writes a failing test before the code, makes it pass, and then improves the code.

In plain words
What is it for?
Use it inside an implementation task to build features one behavior at a time through the red, green, refactor cycle.
Why use it?
It checks each small behavior as it is built and helps catch regressions by running the wider test suite.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter. Also seen: mentions subagents.

Part of the ideal-harness plugin — 10 skills, 4 agents, 3 hooks, 5 MCP servers shipped together

Good fit Use it inside an implementation task to build features one behavior at a time through the red, green, refactor cycle.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/bharat3645/the-ideal-harness/tdd
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.

Any agent
npx skills add bharat3645/The-Ideal-Harness --skill tdd
Clone the repo
git clone --depth 1 https://github.com/bharat3645/The-Ideal-Harness

Made for: Claude Code.

Or install ideal-harness, the plugin that ships this one along with the rest of its 10 skills, 4 agents, 3 hooks, 5 MCP servers.

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 tdd

README.md
[![agentmods](https://agentmods.dev/badge/skills/bharat3645/the-ideal-harness/tdd/github.svg)](https://agentmods.dev/skills/bharat3645/the-ideal-harness/tdd)
Your own site
<a href="https://agentmods.dev/skills/bharat3645/the-ideal-harness/tdd"><img src="https://agentmods.dev/badge/skills/bharat3645/the-ideal-harness/tdd/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for tdd

Your own site · 80×15
<a href="https://agentmods.dev/skills/bharat3645/the-ideal-harness/tdd"><img src="https://agentmods.dev/badge/skills/bharat3645/the-ideal-harness/tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 468 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00062 $0.00468
Opus 5 $0.00031 $0.00234
Sonnet 5 $0.00012 $0.00094
Haiku 4.5 $0.00006 $0.00047

Measured 12d ago against content hash 7c751bb4f0f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

tdd 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 12d 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/tdd/SKILL.md · 35 lines

What it actually says

TDD (red, green, refactor)

subagent-driven-development's ledger verifies a whole TASK is done via verify.command. This skill is the finer-grained discipline for the code written INSIDE one task: prove the test fails for the right reason before making it pass, one small cycle at a time. The two compose — a task's verify.command is often literally "run the test suite this skill was used to write."

Process

  1. Write one test for the next smallest behavior, not the whole feature. Name it for the behavior, not the implementation ("rejects a negative amount", not "test3").
  2. Run it and confirm it fails for the stated reason — a test that passes before the code exists, or fails with an unrelated error, proves nothing. Read the actual failure output.
  3. Write the minimum code to pass it. Resist writing more than the current test demands; the next test will demand the next piece.
  4. Run the full local suite, not just the new test — a green new test next to a broken old one is not progress.
  5. Refactor with the tests green, if the code asks for it. Never refactor and add behavior in the same step — that's two changes wearing one commit.
  6. Repeat from 1.

Boundary

This is a per-change discipline, not a project methodology mandate — some code (glue, config, generated bindings) isn't worth testing this granularly, and this skill doesn't override that judgment. It also isn't a substitute for the ledger's task-level verify.command: a task can pass every unit test this cycle produced and still fail its real acceptance check (e.g. an integration behavior no unit test covers) — the ledger's verify is still the thing that decides "done."

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. 12d ago First seen · 35 lines · 62 tokens per session scan A 7c751bb4f0f0

Subscribe to this mod's changes

tdd is a skill published in the GitHub repository bharat3645/The-Ideal-Harness (5 stars, last pushed 2d ago), licensed MIT. It adds 62 tokens to every session and 468 once invoked, about $0.0003 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.

Related

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