openspec-plus-tdd

openspec-plus-tdd is a skill for Claude Code, Codex from sudokar/openspec-plus. It costs 190 tokens per session (4,306 once invoked), scanned A, original, MIT.

A test-first coding workflow for implementing OpenSpec tasks. TDD, or test-driven development, means writing a failing test, making the code pass, and then reviewing the design before moving to the next case.

In plain words
What is it for?
Use it while implementing OpenSpec change tasks to turn relevant Gherkin acceptance scenarios into tests and apply a separate RED-GREEN-REFACTOR cycle to each case.
Why use it?
It prevents production code from being written without a test showing the required behavior. It also makes acceptance scenarios, edge cases, helper behavior, and error paths explicit.

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/sudokar/openspec-plus/openspec-plus-tdd
Any agent
npx skills add sudokar/openspec-plus --skill openspec-plus-tdd
Clone the repo
git clone --depth 1 https://github.com/sudokar/openspec-plus

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 openspec-plus-tdd

README.md
[![agentmods](https://agentmods.dev/badge/skills/sudokar/openspec-plus/openspec-plus-tdd.svg)](https://agentmods.dev/skills/sudokar/openspec-plus/openspec-plus-tdd)
Your own site
<a href="https://agentmods.dev/skills/sudokar/openspec-plus/openspec-plus-tdd"><img src="https://agentmods.dev/badge/skills/sudokar/openspec-plus/openspec-plus-tdd.svg" alt="Measured on agentmods" height="20"></a>
Per session 190 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,306 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 $0.00190 $0.04306
Opus 5 $0.00095 $0.02153
Sonnet 5 $0.00038 $0.00861
Haiku 4.5 $0.00019 $0.00431

Measured today against content hash c9623d638943, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

openspec-plus-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 today.

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/openspec-plus-tdd/SKILL.md · 378 lines

How it starts

The opening of the file, as written. The whole thing — 378 lines — stays where its author put it; the contents beside it link to each section on GitHub.

OpenSpec Plus TDD

Mission

Strict RED-GREEN-REFACTOR per test for OpenSpec change implementation. Every test — whether derived from a Gherkin scenario relevant to the slice in spec.md, written for a unit, edge case, helper, or error path — goes through its own atomic cycle before the next test begins. Production code exists only to make a previously-failing test pass. Surgical changes, simplicity first, no speculative abstractions, every changed line traces to a slice task.

Gherkin scenarios in spec.md are the canonical source for acceptance tests: every scenario relevant to the slice MUST become at least one test. The implementer is encouraged to add additional tests — unit tests for individual functions, edge-case tests, helper tests, error-path tests — when fast-feedback granularity is valuable. Every test follows the same cycle.

Loaded by openspec-plus-apply (subagent prompt + inline mode) before any code is written.


RIGID. NEVER write production code before a test fails for the right reason. NEVER write tests for multiple cases before the first one is GREEN. NEVER skip the REFACTOR assessment. NEVER mark a task [x] while a relevant test is failing or skipped. NEVER add comments for non-complex logic. NEVER refactor code outside the slice. NEVER write any code (test or production) before reading the project's referenced coding/testing standards. NEVER ship without covering every Gherkin scenario in spec.md with at least one test. Letter and spirit are the same.

Red flags — STOP, you are about to violate this skill:

  • "I'll write the test after, it's faster"
  • "Too simple to need a test"
  • "Manually verified, that's enough"
  • "Gherkin scenario is vague, generic test is fine"
  • "Skip this failing test, circle back later"
  • "Mark .skip to unblock the slice"
  • "While I'm here, clean up the adjacent code"
  • "Add an interface in case we swap implementations"
  • "Short comment explains the obvious"
  • "Error handling for cases that can't happen"
  • "Test passed first run, must be right"
  • "Let me write tests for all the cases first, then implement"
  • "Test 1 done — I have a clear picture, let me write all the rest at once"
  • "I have a clear picture of all 5 cases — let me write them all"
  • "Writing one test at a time is slower"
  • "These cases are related, I'll batch them"
  • "The code I'm about to write covers test 2 anyway, no need to write its test separately first"
  • "Acceptance tests cover the happy path — skip the unit/edge tests"
  • "Scenarios covered, no need to add granular tests even though the helper has edge cases"
  • "Nothing to refactor, skip the assessment"
  • "I know the project conventions, no need to re-read AGENTS.md"
  • "AGENTS.md has many rules — I'll apply the ones that feel relevant"

Read the full file on GitHub · 378 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. today Changed · +1 lines c9623d638943
  2. 4d ago First seen · 377 lines · 190 tokens per session scan A 7eac3da809f1

Subscribe to this mod's changes

openspec-plus-tdd is a skill published in the GitHub repository sudokar/openspec-plus (166 stars, last pushed today), licensed MIT. It adds 190 tokens to every session and 4,306 once invoked, about $0.0010 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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