tdd-runner

tdd-runner is an agent for Claude Code from jhlee0409/omni-harness-kit. It costs 126 tokens per session (505 once invoked), scanned A, original, MIT.

An agent that follows test-driven development, or TDD: it writes a failing test, adds the smallest code change to pass it, and then cleans up the code while keeping the test passing.

In plain words
What is it for?
Use it for one behavior change at a time when you want the implementation built and verified test-first.
Why use it?
It provides evidence that the requested behavior was missing, was implemented, and still works after refactoring.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the harness-kit plugin — 18 skills, 28 agents, 2 hooks shipped together

Good fit Use it for one behavior change at a time when you want the implementation built and verified test-first.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/jhlee0409/omni-harness-kit/tdd-runner
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.

Clone the repo
git clone --depth 1 https://github.com/jhlee0409/omni-harness-kit

Made for: Claude Code.

Or install harness-kit, the plugin that ships this one along with the rest of its 18 skills, 28 agents, 2 hooks.

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-runner

README.md
[![agentmods](https://agentmods.dev/badge/agents/jhlee0409/omni-harness-kit/tdd-runner/github.svg)](https://agentmods.dev/agents/jhlee0409/omni-harness-kit/tdd-runner)
Your own site
<a href="https://agentmods.dev/agents/jhlee0409/omni-harness-kit/tdd-runner"><img src="https://agentmods.dev/badge/agents/jhlee0409/omni-harness-kit/tdd-runner/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-runner

Your own site · 80×15
<a href="https://agentmods.dev/agents/jhlee0409/omni-harness-kit/tdd-runner"><img src="https://agentmods.dev/badge/agents/jhlee0409/omni-harness-kit/tdd-runner.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 126 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 505 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 $0.00126 $0.00505
Opus 5 $0.00063 $0.00253
Sonnet 5 $0.00025 $0.00101
Haiku 4.5 $0.00013 $0.00051

Measured 8d ago against content hash 0bcc99a3bae0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

tdd-runner 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 8d 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.

agents/tdd-runner.md · 42 lines

What it actually says

You own one red → green → refactor cycle for a single behavior and return the result with real evidence.

Loop

  1. Scope the ONE behavior to change. If asked for several, do the first and report; don't batch.
  2. 🔴 Red — write the smallest failing test. Run it with the repo's test command (from .claude/harness-kit.json verify_command, or detect it). Confirm it FAILS for the right reason (the missing behavior, not a typo / import error). Capture the failing output.
  3. 🟢 Green — minimum implementation to pass. Re-run; capture the passing output.
  4. 🔵 Refactor — remove duplication / improve names with the test green; re-run; stay green. Structural ≠ behavioral — don't mix.

Output (BLUF)

  • Verdict: GREEN (with evidence) / BLOCKED (why — e.g. can't run the test).
  • Behavior: one line.
  • Red evidence: the failing run output (the assertion that failed).
  • Green evidence: the passing run output (counts).
  • Refactor: what was cleaned, still green.
  • Files: the test + impl paths changed.

Constraints

  • Never write implementation before a failing test exists for it.
  • A test that passes on first run, or fails for the wrong reason, is not red — fix the test before implementing.
  • The evidence is a REAL run (show the output), never "tests pass" asserted.
  • One behavior per run; keep the step small.
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. 8d ago First seen · 42 lines · 126 tokens per session scan A 0bcc99a3bae0

Subscribe to this mod's changes

tdd-runner is an agent published in the GitHub repository jhlee0409/omni-harness-kit (2 stars, last pushed 1mo ago), licensed MIT. It adds 126 tokens to every session and 505 once invoked, about $0.0006 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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