Borrowing it
Nothing to install: this file belongs to opagani/cassini-workshop. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/opagani/cassini-workshop/main/.claude/skills/bdd-specs/SKILL.mdgit clone --depth 1 https://github.com/opagani/cassini-workshopWrote 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.
[](https://agentmods.dev/skills/opagani/cassini-workshop/bdd-specs)<a href="https://agentmods.dev/skills/opagani/cassini-workshop/bdd-specs"><img src="https://agentmods.dev/badge/skills/opagani/cassini-workshop/bdd-specs/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.
<a href="https://agentmods.dev/skills/opagani/cassini-workshop/bdd-specs"><img src="https://agentmods.dev/badge/skills/opagani/cassini-workshop/bdd-specs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00183 | $0.01708 |
| Opus 5 | $0.00092 | $0.00854 |
| Sonnet 5 | $0.00037 | $0.00342 |
| Haiku 4.5 | $0.00018 | $0.00171 |
Grade A, and why
bdd-specs 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.
This is a copy
100% identical to bdd-specs — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 163 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Behavior-Driven Design — Specifications First
Specifications are written before implementation. The spec is the design artifact: it encodes the intended behavior from the plan and the user stories, fails first, and is the definition of done. Do not write implementation code under this skill until the specs exist and the user has seen them.
🎯 Why: Design for Change
The goal of writing software is to be able to change it safely. Specs are the safety net that makes change possible — without them, every edit is a guess. One assertion per Specification means a failing spec names exactly what broke; happy/sad-path separation means you can change one behavior without re-reading the whole suite. The spec suite is the change-budget for the codebase.
The non-negotiable workflow
Run these gates in order. Do not skip ahead.
1. Require the plan
Look for the build plan at /docs/PLAN.md (also accept
docs/PLAN.md, PLAN.md, or an obvious docs/plan.*).
- If it is missing: stop. Ask the user to provide a
PLAN.mdin/docs. Offer to scaffold one fromtemplates/PLAN.mdand let them fill it in, or to draft it from their description and write it to/docs/PLAN.mdfor approval. Do not proceed to specs without an approved plan. - If it exists: read it fully. It defines the features and the technical boundaries the specs must cover.
2. Require the user stories
Look for user stories at /docs/STORIES.md (also accept
docs/STORIES.md, STORIES.md).
- If it is missing: stop. Ask the user for the user stories. Offer
to scaffold
templates/STORIES.md, or to derive draft stories fromPLAN.mdand write them to/docs/STORIES.mdfor approval. Do not proceed without stories — they are the source of every Scenario. - If it exists: read it fully. Each story maps to one Feature; each acceptance criterion / "so that" outcome maps to a Scenario.
3. Detect the test runner
Pick the runner from the project, do not ask:
What ships with it
6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 8d ago First seen · 163 lines · 183 tokens per session scan A 0ebc2a40b557
bdd-specs is a skill published in the GitHub repository opagani/cassini-workshop (0 stars, last pushed 2mo ago), licensed MIT. It adds 183 tokens to every session and 1,708 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to bdd-specs, differing in 0 lines, and is treated as a copy.
Other skills, from other repositories
implement
Implement a specification using a TDD-oriented workflow. Extracts requirements, generates tests first, then implements to pass the tests. Includes spiral detection and acceptance gates.
dev-pipeline
Issue → Explore → Plan → TDD (Red→Green→Refactor) → Benchmark → PR → Review.
test-driven-development
Test-Driven Development enforces the RED-GREEN-REFACTOR discipline on every code change an agent produces.
prespec
Write the behaviour specification for a feature BEFORE implementing it, as test cases. Use whenever you are about to build a new endpoint, screen, flow, or behaviour — especially anything touching auth, sessions, tokens, lists, or pagination. Also use when asked "how should I test this", "what should this actually…
Test Driven Development
Strict Red-Green-Refactor implementation methodology for high quality, regression-free software.
api-testing
Testing patterns for MCP tool/resource handlers using createMockContext and Vitest. Covers mock context options, handler testing, McpError assertions, format testing, Vitest config setup, and test isolation conventions.