atdd

A workflow for turning approved acceptance criteria into a standard Given/When/Then specification and a test pipeline for the project. Acceptance criteria are the agreed conditions that define when a feature works.

In plain words
What is it for?
Writing a feature's acceptance specifications and generating its project-specific acceptance-test pipeline after acceptance criteria have been decided.
Why use it?
It provides a concrete, executable form of the required behavior and connects it to the project's testing tools.

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/swingerman/engineer/atdd
Any agent
npx skills add swingerman/engineer --skill atdd
Clone the repo
git clone --depth 1 https://github.com/swingerman/engineer

Made for: Claude Code, Codex.

Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,170 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 $0.00076 $0.01170
Opus 5 $0.00038 $0.00585
Sonnet 5 $0.00015 $0.00234
Haiku 4.5 $0.00008 $0.00117

Measured 2d ago against content hash 656364a69409, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

atdd 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.

engineer/skills/atdd/SKILL.md · 93 lines

How it starts

The opening of the file, as written. The whole thing — 93 lines — stays where its author put it; the contents beside it link to each section on GitHub.

atdd

The DAE pipeline's Checkpoint 3 (Spec) entry point. AC discovery (Checkpoint 2, discover-acs) decided what behaviors must work; this step formalizes them as a standard-Gherkin spec.md and generates the project-specific test pipeline.

This skill is a thin bridge: the acceptance workflow itself lives in the atdd plugin (atdd:atdd). engineer.atdd wraps it with the DAE checkpoint contract — the entry gate in, the handoff out — so the acceptance pipeline is a first-class checkpoint of the engineer pipeline rather than a separate detour.

Requires the atdd plugin. If it is not installed, tell the user to run /plugin install atdd@disciplined-agentic-engineering and stop.

When to use

Checkpoint 3, after discover-acs (Checkpoint 2) has produced an approved acs.md. Produces spec.md + the feature's .build/ pipeline.

Not for: AC discovery (discover-acs); planning (plan); using the acceptance workflow outside a DAE feature folder (invoke atdd:atdd directly).

Workflow

Step 0 — Entry gate

Verify the prior checkpoint is complete: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_handoff.py <feature-dir> --through 2. On a non-zero exit, stop and surface the gap to the human.

Verify branch hygiene: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_branch.py <feature-dir>. On a non-zero exit, stop and surface the message to the human — switch branches and re-invoke. The check honors the git.manual: true manifest opt-out.

After the gate passes, show the pipeline breadcrumb: run ${CLAUDE_PLUGIN_ROOT}/scripts/dae_progress.py <feature-dir> and present its output to the human — it shows where this checkpoint sits in the DAE pipeline. The breadcrumb is advisory: a non-zero exit or a missing progress.md never blocks the skill. Then create one TodoWrite todo per workflow step below. See ${CLAUDE_PLUGIN_ROOT}/references/progress-indicator.md.

Step 1 — Run the acceptance workflow

Invoke the atdd:atdd skill, scoped to this feature: write the feature's spec.md in standard Gherkin from acs.md, then generate the test pipeline (the pipeline-builder agent + the portable dae_gherkin.py parser). Present spec.md to the human for approval — specs are the human's contract.

Read the full file on GitHub · 93 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. 2d ago First seen · 93 lines · 76 tokens per session scan A 656364a69409

Subscribe to this mod's changes

atdd is a skill published in the GitHub repository swingerman/engineer (144 stars, last pushed 6d ago), licensed MIT. It adds 76 tokens to every session and 1,170 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 2026-08-30.

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