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Official agent skill

Principle Test Behavior Not Implementation

by cursor in cursor/plugins

Apply when you write, change, or keep a test. An agent skill from cursor/plugins.

OfficialNo licenceAuto-check passed

Install Principle Test Behavior Not Implementation

skills CLI
$ npx skills add cursor/plugins --skill principle-test-behavior-not-implementation -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install cursor/plugins principle-test-behavior-not-implementation --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/cursor/plugins.git skills-src && mkdir -p .claude/skills && cp -r skills-src/pstack/skills/principle-test-behavior-not-implementation .claude/skills/principle-test-behavior-not-implementation && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
principle-test-behavior-not-implementation
GitHub stars
10k
Used in
2 other repos
Token cost
~644 tokens
SKILL.md length
319 words
Files
1
Skills in repo
99
Repo updated
First seen
Licence
None found

At a glance

Apply when you write, change, or keep a test. An agent skill from cursor/plugins.

  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Principle Test Behavior Not Implementation is an agent skill from cursor/plugins, published by the product's own GitHub organization. Apply when you write, change, or keep a test. Call the code the way its users do and assert the result they observe against a literal expected value. If the test would still pass when every imported function returns undefined, rewrite the assertion or delete the test.

Its SKILL.md is about 640 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: Cursor plugin specification and official plugins.

Example prompts

  • “/principle-test-behavior-not-implementation”

What it can do on your machine

Read from SKILL.md and the folder at commit 9f451cf. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Principle Test Behavior Not Implementation loads about 644 tokens when it runs. Until then it costs about 78 tokens; SKILL.md has 319 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~78
When it runs · the whole SKILL.md, loaded when a task matches
~644

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

Without a licence we can't republish the file, so here is its outline and opening line. It has 319 words (~644 tokens).

“A test calls the code the way its users do and asserts the result they observe against a literal expected value. A test that asserts which calls the code made, or restates a constant the code contains, does neither.”

— opening of SKILL.md by cursor
name
principle-test-behavior-not-implementation
disable-model-invocation
true

Read the full SKILL.md on GitHub

Files

Just SKILL.md in pstack/skills/principle-test-behavior-not-implementation of cursor/plugins.

Open the folder on GitHubat commit 9f451cf

Used in 2 other repositories

We found 2 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 2 other GitHub owners. This page covers the copy in cursor/plugins, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Principle Test Behavior Not Implementation next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Principle Test Behavior Not Implementation compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Principle Test Behavior Not Implementation this skillcursor/plugins10k2 repos~644Automated safety check: PassNone
Uxui Principlessickn33/agentic-awesome-skills47k2 repos~548Automated safety check: PassMIT
First Principles Thinkingmindfold-ai/Trellis15k—~4.1kAutomated safety check: PassMIT
Keep Trackdavidondrej/skills4.1k—~132Automated safety check: PassMIT
Editorial Burgundy Principles Templatenexu-io/open-design100k—~461Automated safety check: PassApache-2.0
Design PrinciplesOwl-Listener/designer-skills2.9k1 repos~300Automated safety check: PassMIT

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Questions about Principle Test Behavior Not Implementation

What does Principle Test Behavior Not Implementation do?

Apply when you write, change, or keep a test. An agent skill from cursor/plugins. Principle Test Behavior Not Implementation is an agent skill from cursor/plugins, published by the product's own GitHub organization. Apply when you write, change, or keep a test.

How do I install Principle Test Behavior Not Implementation in Claude Code?

Run `npx skills add cursor/plugins --skill principle-test-behavior-not-implementation -a claude-code`. Or copy the skill folder (pstack/skills/principle-test-behavior-not-implementation in cursor/plugins) into .claude/skills/principle-test-behavior-not-implementation in your project. Claude Code loads it when a task matches its description.

How do I install Principle Test Behavior Not Implementation in Codex?

Run `npx skills add cursor/plugins --skill principle-test-behavior-not-implementation -a codex`. Or copy the skill folder (pstack/skills/principle-test-behavior-not-implementation in cursor/plugins) into .agents/skills/principle-test-behavior-not-implementation in your project. Codex loads it when a task matches its description.

Can I use Principle Test Behavior Not Implementation in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add cursor/plugins --skill principle-test-behavior-not-implementation -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/principle-test-behavior-not-implementation, .gemini/skills/principle-test-behavior-not-implementation, .github/skills/principle-test-behavior-not-implementation and .opencode/skills/principle-test-behavior-not-implementation in your project.

What does Principle Test Behavior Not Implementation need to run?

SKILL.md names no scripts, command-line tools or credentials: Principle Test Behavior Not Implementation is instructions for the agent only.

Does Principle Test Behavior Not Implementation access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Principle Test Behavior Not Implementation safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Principle Test Behavior Not Implementation use?

No licence was found for Principle Test Behavior Not Implementation or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.

How many tokens does Principle Test Behavior Not Implementation use?

About 644 tokens (SKILL.md is roughly 2.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Principle Test Behavior Not Implementation?

Skills that share tags, products or a category with Principle Test Behavior Not Implementation: Uxui Principles (sickn33/agentic-awesome-skills, 47k stars), First Principles Thinking (mindfold-ai/Trellis, 15k stars), Keep Track (davidondrej/skills, 4.1k stars) and Editorial Burgundy Principles Template (nexu-io/open-design, 100k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Principle Test Behavior Not Implementation?

cursor (a GitHub organization, an official publisher) maintains it in cursor/plugins, which has 10,130 GitHub stars. The repository holds 99 skills in this directory. The repository was last updated on October 6, 2026.

Source: cursor/plugins on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.