Agent skill

Vitest Best Practices

Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization.

MITAuto-check passedTesting & QA

Install Vitest Best Practices

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a claude-code

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

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices --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/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agent/skills/vitest-best-practices .claude/skills/vitest-best-practices && 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/

Paste into Claude Code

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .claude/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agent/skills/vitest-best-practices .agents/skills/vitest-best-practices && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .agents/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agent/skills/vitest-best-practices .cursor/skills/vitest-best-practices && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .cursor/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/PageAI-Pro/ralph-loop.git --path .agent/skills/vitest-best-practices

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agent/skills/vitest-best-practices .gemini/skills/vitest-best-practices && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .gemini/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agent/skills/vitest-best-practices .github/skills/vitest-best-practices && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .github/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install PageAI-Pro/ralph-loop vitest-best-practices --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/PageAI-Pro/ralph-loop.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agent/skills/vitest-best-practices .opencode/skills/vitest-best-practices && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "vitest-best-practices" agent skill from https://github.com/PageAI-Pro/ralph-loop/tree/main/.agent/skills/vitest-best-practices into .opencode/skills/vitest-best-practices/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest-best-practices", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: vitest-best-practices
GitHub stars: 315
Token cost: ~1.2k tokens
SKILL.md length: 426 words
Files: 12 (incl. references)
Skills in repo: 4
Repo updated: Aug 31, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization.

Works in 3 steps: Start with the Overview (AGENTS.md) → Load Specific Rules as Needed → Apply the Pattern
Refactoring vitest tests
SKILL.md covers When to Apply This Skill, Do NOT Use This Skill When, What This Skill Covers and How to Use, plus 2 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Vitest Best Practices is an agent skill from PageAI-Pro/ralph-loop. Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization. Use when writing, reviewing, or refactoring vitest tests, or when user mentions vitest, testing, TDD, test coverage, mocking, assertions, or test files (.test.ts, .spec.ts).

Its SKILL.md is about 1.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 12 other files, including reference files (for example `AGENTS.md`, `references/aaa-pattern.md` and `references/assertions.md`). Compatibility notes: Requires vitest testing framework

It sits in Testing & QA, covering Unit testing. It works with Vitest. The repository describes itself as: A long-running AI agent loop. Ralph automates software development tasks by iteratively working through a task list until completion. The licence is MIT.

When your agent uses it

Refactoring vitest tests
User mentions vitest
Test files (.test.ts

Example prompts

“/vitest-best-practices”

Requirements

Compatibility (from SKILL.md): Requires vitest testing framework

Workflow steps

3 steps, taken from the step headings in SKILL.md.

Start with the Overview (AGENTS.md)
Load Specific Rules as Needed
Apply the Pattern

What it can do on your machine

Read from SKILL.md and the folder at commit eba65eb. 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 (its code samples are typescript).
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.
Compatibility
Requires vitest testing framework
From compatibility in the SKILL.md frontmatter.

Context cost

Vitest Best Practices loads about 1.2k tokens when it runs, and up to ~26k if it reads all its reference files. Until then it costs about 98 tokens; SKILL.md has 426 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~98
When it runs · the whole SKILL.md, loaded when a task matches: ~1.2k
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~26k

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

The full file from PageAI-Pro/ralph-loop at commit eba65eb, republished under its MIT licence (© PageAI-Pro). 426 words, ~1,220 tokens.

Download SKILL.mdSave it as .claude/skills/vitest-best-practices/SKILL.md (or your agent's skills folder). This skill also uses 11 other files; get the full folder from GitHub.

name: vitest-best-practices
description: Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization. Use when writing, reviewing, or refactoring vitest tests, or when user mentions vitest, testing, TDD, test coverage, mocking, assertions, or test files (*.test.ts, *.spec.ts).
compatibility: Requires vitest testing framework

Vitest Best Practices

When to Apply This Skill

Use this skill when you encounter any of these scenarios:

File Patterns

Working with *.test.ts, *.spec.ts, or similar test files
Creating new test files for TypeScript/JavaScript modules
Reviewing existing vitest test suites

User Intent Keywords

User mentions: vitest, testing, TDD, BDD, unit tests, integration tests
User asks to: write tests, add test coverage, fix failing tests, refactor tests
User discusses: mocking, stubbing, assertions, test performance, test organization

Code Context

Files importing from vitest (describe, it, expect, vi)
Test setup/teardown code (beforeEach, afterEach, beforeAll, afterAll)
Mock/spy implementations using vi.mock(), vi.spyOn(), vi.fn()
Assertion chains (expect(...).toEqual(), .toBe(), .toThrow(), etc.)

Common Tasks

Writing new test cases for existing functionality
Refactoring tests for better clarity or performance
Debugging flaky or failing tests
Improving test coverage or maintainability
Reviewing test code for best practices compliance

Do NOT Use This Skill When

Writing end-to-end tests with Playwright/Cypress (different scope)
The task is purely about implementation code, not tests

What This Skill Covers

This skill provides comprehensive guidance on:

Test Organization: File placement, naming conventions, grouping strategies
AAA Pattern: Arrange, Act, Assert structure for clarity
Parameterized Tests: Using it.each() for testing variations
Error Handling: Testing exceptions, edge cases, and fault injection
Assertions: Choosing strict assertions (toEqual, toStrictEqual, toThrow)
Test Doubles: Fakes, stubs, mocks, spies - when to use each
Async Testing: Promises, async/await, timers, and concurrent tests
Performance: Fast tests, avoiding expensive operations, cleanup patterns
Vitest-Specific Features: Coverage, watch mode, benchmarking, type testing, setup files
Snapshot Testing: When and how to use snapshots effectively

Show full SKILL.md (163 more words)Show less

How to Use

This skill uses a progressive disclosure structure to minimize context usage:

1. Start with the Overview (AGENTS.md)

Read AGENTS.md for a concise overview of all rules with one-line summaries.

2. Load Specific Rules as Needed

When you identify a relevant optimization, load the corresponding reference file for detailed implementation guidance:

Core Patterns:

Advanced Topics:

3. Apply the Pattern

Each reference file contains:

❌ Incorrect examples showing the anti-pattern
✅ Correct examples showing the optimal implementation
Explanations of why the pattern matters

Quick Example

This skill helps you transform unclear tests into clear, maintainable ones:

Before (unclear):

test('product test', () => {
  const p = new ProductService().add({name: 'Widget'});
  expect(p.status).toBe('pendingApproval');
});

After (optimized with this skill):

describe('ProductService', () => {
  describe('Add new product', () => {
    it('should have status "pending approval" when no price is specified', () => {
      // Arrange
      const productService = new ProductService();

      // Act
      const newProduct = productService.add({name: 'Widget'});

      // Assert
      expect(newProduct.status).toEqual('pendingApproval');
    });
  });
});

Key Principles

Clarity over cleverness: Tests should be instantly understandable
Flat structure: Avoid deep nesting in describe blocks
One assertion per concept: Focus tests on single behaviors
Strict assertions: Prefer toEqual over toBe, toStrictEqual when needed
Minimal mocking: Use real implementations when practical
Fast execution: Keep tests quick through efficient setup/teardown

Files

SKILL.md and 11 other files (references) in .agent/skills/vitest-best-practices of PageAI-Pro/ralph-loop.

SKILL.md
AGENTS.md
references/aaa-pattern.md
references/assertions.md
references/async-testing.md
references/error-handling.md
references/organization.md
references/parameterized-tests.md
references/performance.md
references/snapshot-testing.md
references/test-doubles.md
references/vitest-features.md

Open the folder on GitHubat commit eba65eb

Compare with similar skills

Vitest Best Practices 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.

Vitest Best Practices compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Vitest Best Practices this skillPageAI-Pro/ralph-loop	315	—	~1.2k	Automated safety check: Pass	MIT	1 mo ago
Test Writing WorkflowiOfficeAI/AionUi	33k	1 repos	~1.2k	Automated safety check: Pass	Apache-2.0	1 mo ago
Vitestsupabase/supabase	111k	12 repos	~1.1k	Automated safety check: Pass	Apache-2.0	yesterday
Test GuardamElnagdy/guard-skills	1.3k	2 repos	~2.1k	Automated safety check: Pass	MIT	3 mo ago
Adding LLM MCP ToolsTriliumNext/Trilium	38k	—	~2.5k	Automated safety check: Pass	AGPL-3.0	yesterday
Concept Page Test Writerleonardomso/33-js-concepts	67k	—	~5.5k	Automated safety check: Pass	MIT	1 mo ago

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Questions about Vitest Best Practices

What does Vitest Best Practices do?

Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization. Vitest Best Practices is an agent skill from PageAI-Pro/ralph-loop. Comprehensive vitest testing patterns covering test structure, AAA pattern, parameterized tests, assertions, mocking, test doubles, error handling, async testing, and performance optimization.

When should I use Vitest Best Practices?

Vitest Best Practices fits situations like: refactoring vitest tests; user mentions vitest; test files (.test.ts.

How do I install Vitest Best Practices in Claude Code?

Run `npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a claude-code`. Or copy the skill folder (.agent/skills/vitest-best-practices in PageAI-Pro/ralph-loop) into .claude/skills/vitest-best-practices in your project. Claude Code loads it when a task matches its description.

How do I install Vitest Best Practices in Codex?

Run `npx skills add PageAI-Pro/ralph-loop --skill vitest-best-practices -a codex`. Or copy the skill folder (.agent/skills/vitest-best-practices in PageAI-Pro/ralph-loop) into .agents/skills/vitest-best-practices in your project. Codex loads it when a task matches its description.

Can I use Vitest Best Practices 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 PageAI-Pro/ralph-loop --skill vitest-best-practices -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/vitest-best-practices, .gemini/skills/vitest-best-practices, .github/skills/vitest-best-practices and .opencode/skills/vitest-best-practices in your project.

What does Vitest Best Practices need to run?

SKILL.md names no scripts, command-line tools or credentials: Vitest Best Practices is instructions for the agent only. Compatibility (from SKILL.md): Requires vitest testing framework.

Does Vitest Best Practices 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 Vitest Best Practices 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 Vitest Best Practices use?

Vitest Best Practices is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Vitest Best Practices use?

About 1.2k tokens (SKILL.md is roughly 4.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 25k tokens, read only when the agent opens those files.

What are the alternatives to Vitest Best Practices?

Skills that share tags, products or a category with Vitest Best Practices: Test Writing Workflow (iOfficeAI/AionUi, 33k stars), Vitest (supabase/supabase, 111k stars), Test Guard (amElnagdy/guard-skills, 1.3k stars) and Adding LLM MCP Tools (TriliumNext/Trilium, 38k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Vitest Best Practices?

PageAI-Pro (a GitHub organization) maintains it in PageAI-Pro/ralph-loop, which has 315 GitHub stars. The repository holds 4 skills in this directory. The repository was last updated on August 31, 2026.

Source: PageAI-Pro/ralph-loop on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Vitest Best Practices

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Compatibility

Context cost

Safety

SKILL.md

Vitest Best Practices

When to Apply This Skill

File Patterns

User Intent Keywords

Code Context

Common Tasks

Do NOT Use This Skill When

What This Skill Covers

How to Use

1. Start with the Overview (AGENTS.md)

2. Load Specific Rules as Needed

3. Apply the Pattern

Quick Example

Key Principles

Files

Compare with similar skills

Similar skills

More from PageAI-Pro/ralph-loop

Related

Questions about Vitest Best Practices