Behavior-Driven Development Agent Skill

Behavior-Driven Development as a collaboration and specification practice, with pytest-bdd and behave as the bundled automation references.

Context cost
6.9k tokensestimated from the bundle, loaded when it triggers
Bundle
7 files · 27.6 kBtext throughout, nothing executable
Licence
Apache-2.0the author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

Behavior-Driven Development as a collaboration and specification practice, with pytest-bdd and behave as the bundled automation references. Use when defining behavior through concrete examples or acceptance criteria, writing or reviewing Gherkin .feature files, wiring pytest-bdd or behave step definitions, or checking that tests still express business behavior rather than implementation.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

pytestsecuritytesting

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md4.6 kB · preview
--- name: bdd ---
6# Behavior-Driven Development
7
8BDD builds shared understanding of a problem through concrete examples, written in business language, agreed before implementation. The examples become executable specifications; running them drives the code. The order is fixed: **conversation first, capture second, automation last**. A team running Gherkin without the conversation has test automation, not BDD.
9
10Two automation layers are bundled: [pytest-bdd](references/pytest-bdd.md) and [behave](references/behave.md). The practice and the Gherkin carry to any stack — see [Other automation layers](#other-automation-layers).
11
12## Preflight: does this deserve Gherkin?
13
14Gate every "add a BDD test" impulse:
15
16- The behavior is stable and business-meaningful — not scaffolding, framework glue, or an implementation still finding its shape.
17- The sentence helps someone imagine a real use of this project. A scenario that reads as a natural-language translation of a technical test gets rewritten, or dropped in favor of a plain pytest test.
18
19## Workflow
20
211. **Discover.** Write down Who / What / Why, the business rules, examples, and open questions — before touching a test framework. Done when every rule carries at least one positive and one negative example and every unknown is a recorded question rather than a guess. Working solo, simulate the Three Amigos using subagents (business, development, quality) and mark which points are inference needing user confirmation. Detail and templates: [practice.md](references/practice.md).
222. **Formulate.** Invoke the write-simply skill (via the Skill tool) — the Gherkin and the prose presenting it follow its register. Draft the scenarios — Given context, When event, Then observable outcome — in domain language. Ask the user for approval, then run every scenario through the quality gate below before writing any glue code. Syntax and style: [gherkin.md](references/gherkin.md).
233. **Automate** — only when the user asks for implementation. The framework is a project fact — check the declared dependencies for behave or pytest-bdd (a features/steps/ tree with environment.py means behave) and join what is there. Only greenfield picks, and Gherkin authorship decides: developers write it and domain experts review → pytest-bdd inside the existing pytest suite; the business writes the feature files themselves → behave, where they run standalone. Mechanics: [pytest-bdd.md](references/pytest-bdd.md) / [behave.md](references/behave.md). Bind scenarios, watch the run fail first, write the smallest code that passes.
244. **Refactor.** Keep scenario language stable while extracting helpers and fixtures; add boundary examples and counterexamples; report the red→green evidence and unresolved questions.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md637 words
Files7
LicenceApache-2.0
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈110
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
6,790
on trigger
The instruction body and 6 supporting files, read only when the skill fires.
3.5%
of a 200k window
Ten skills this size would take about 35% of the window before you open a file.
050k100k150k200k context window

6.9k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

7 files, 27.6 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md4.6 kB
  • deps.yml0.1 kB
  • README.md2.7 kB
  • references/behave.md5.5 kB
  • references/gherkin.md6.3 kB
  • references/practice.md2.5 kB
  • references/pytest-bdd.md5.9 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 7 files you can review in full before installing. The Apache-2.0 licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Behavior-Driven Development · 6.9k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/behavior-driven-development/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/behavior-driven-development" ] && { [ ! -e .claude/skills/behavior-driven-development ] || { mv .claude/skills/behavior-driven-development "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/behavior-driven-development" .claude/skills/ && echo "Installed .claude/skills/behavior-driven-development"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add yassimba/behavior-driven-development

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/behavior-driven-development/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/behavior-driven-development/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/behavior-driven-development" ] && { [ ! -e ~/.claude/skills/behavior-driven-development ] || { mv ~/.claude/skills/behavior-driven-development "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/behavior-driven-development" ~/.claude/skills/ && echo "Installed ~/.claude/skills/behavior-driven-development" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/behavior-driven-development/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as bdd in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, behavior-driven-development.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referenceyassimba/behavior-driven-development

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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Who wrote it

YA
Yassimba

Publishes on mcprush.

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