df-tdd-developer

df-tdd-developer is a skill for Claude Code, Codex from OneDro1d/dark-factory. It costs 72 tokens per session (1,192 once invoked), scanned A, original, Apache-2.0.

A test-first development guide for building services in Go or Python. It uses the RED-GREEN-REFACTOR cycle: write a failing test, make it pass with minimal code, then improve the code.

In plain words
What is it for?
Writing unit and integration tests while implementing a service. It covers invalid inputs, shared rules, state changes, successful cases, edge cases, and failures.
Why use it?
It turns stated validation rules and scenarios into tests instead of leaving developers to guess what to test. This helps prevent unrequested behavior and catches regressions before handoff.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Writing unit and integration tests while implementing a service. It covers invalid inputs, shared rules, state changes, successful cases, edge cases, and failures.

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Install with agentmods
npx agentmods add skills/onedro1d/dark-factory/df-tdd-developer
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 OneDro1d/dark-factory --skill df-tdd-developer
Clone the repo
git clone --depth 1 https://github.com/OneDro1d/dark-factory

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 df-tdd-developer

README.md
[![agentmods](https://agentmods.dev/badge/skills/onedro1d/dark-factory/df-tdd-developer.svg)](https://agentmods.dev/skills/onedro1d/dark-factory/df-tdd-developer)
Your own site
<a href="https://agentmods.dev/skills/onedro1d/dark-factory/df-tdd-developer"><img src="https://agentmods.dev/badge/skills/onedro1d/dark-factory/df-tdd-developer.svg" alt="Measured on agentmods" height="20"></a>
Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,192 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 $0.00072 $0.01192
Opus 5 $0.00036 $0.00596
Sonnet 5 $0.00014 $0.00238
Haiku 4.5 $0.00007 $0.00119

Measured 7d ago against content hash babffaf6f320, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

df-tdd-developer 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 7d 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/df-tdd-developer/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.

Dark Factory — TDD Developer

Overview

Build every service test-first: RED → GREEN → REFACTOR, one case at a time. Each test is an executable validation rule. The Developer owns unit + integration tests (green before handoff); QA owns E2E + holdout.

The loop

Step Do Done when
RED Pick one case. Write the smallest test that encodes it. Run it — it fails. Fails for the right reason (missing behaviour, not a typo).
GREEN Write the minimal code to pass. Honour the contract; no extra features. New test passes, all existing tests still green.
REFACTOR Improve structure (names, duplication, size) without changing behaviour. Re-run after each change. Still green, cleaner. A red test = you changed behaviour → undo.

Where the test list comes from (don't invent it)

  • LOCAL validation rule → unit test: feed bad input at the edge, assert it is rejected.
  • GLOBAL validation rule → integration/reconciliation test: assert the invariant + the authority tie-break.
  • PO Test Scenario (State 0 → Trigger → State 1) → unit/integration test asserting the end state (happy/edge/failure).
  • effect transform → idempotency test (replay → one action) + compensation test (failure → clean rollback).
  • pure transform → plain input → output unit test.

Blind synthesis (anti-Goodhart)

Your own tests drive your build loop, but the acceptance evidence (PO Test Scenarios, the QA held-back acceptance suite) is withheld from you — you're verified against cases you never saw, which proves you built the spec, not your own test. Don't build to the holdout: if known_input: return known_answer is the lookup-degeneration failure.

GREEN discipline

Minimal code only; honour the exact contracts (no invented schemas); Log.Warn not Log.Error (panics in this stack's shared messaging library); decimal for money; config over code.

⚠️ That logging rule is an instance, not a universal. Some libraries escalate an error-level call into a panic or a process exit, so a defensive Log.Error in a handler takes the service down on the first bad message — the opposite of what the author meant. Others do nothing of the kind. Check what your own stack does and write the answer into your own guidance; the rule above is kept because a reader who follows it on a stack that behaves this way is saved, and one who does not know to ask is not.

Read the full file on GitHub · 86 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. 7d ago First seen · 86 lines · 72 tokens per session scan A babffaf6f320

Subscribe to this mod's changes

df-tdd-developer is a skill published in the GitHub repository OneDro1d/dark-factory (0 stars, last pushed today), licensed Apache-2.0. It adds 72 tokens to every session and 1,192 once invoked, about $0.0004 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 2026-09-01.