vitest
Vitest fast unit testing framework powered by Vite with Jest-compatible API. Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/onmax/nuxt-skills --skill vitest- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads vitest automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Vitest is a next-generation testing framework powered by Vite. It provides a Jest-compatible API with native ESM, TypeScript, and JSX support out of the box. Vitest shares the same config, transformers, resolvers, and plugins with your Vite app.
Key Features:
- Vite-native: Uses Vite's transformation pipeline for fast HMR-like test updates
- Jest-compatible: Drop-in replacement for most Jest test suites
- Smart watch mode: Only reruns affected tests based on module graph
- Native ESM, TypeScript, JSX support without configuration
- Multi-threaded workers for parallel test execution
- Built-in coverage via V8 or Istanbul
- Snapshot testing, mocking, and spy utilities
The skill is based on Vitest 5.0.1, generated at 2026-09-25.
Core
| Topic | Description | Reference |
|---|---|---|
| Configuration | Vitest and Vite config integration, defineConfig usage | core-config |
| CLI | Command line interface, commands and options | core-cli |
| Test API | test/it function, modifiers like skip, only, concurrent | core-test-api |
| Describe API | describe/suite for grouping tests and nested suites | core-describe |
| Expect API | Assertions with toBe, toEqual, matchers and asymmetric matchers | core-expect |
| Hooks | beforeEach, afterEach, beforeAll, afterAll, aroundEach | core-hooks |
Features
| Topic | Description | Reference |
|---|---|---|
| Mocking | Mock functions, modules, timers, dates with vi utilities | features-mocking |
| Snapshots | Snapshot testing with toMatchSnapshot and inline snapshots | features-snapshots |
| Coverage | Code coverage with V8 or Istanbul providers | features-coverage |
| Test Context | Test fixtures, context.expect, test.extend for custom fixtures | features-context |
| Concurrency | Concurrent tests, parallel execution, sharding | features-concurrency |
| Filtering | Filter tests by name, file patterns, tags | features-filtering |
| Test Tags | Label tests with tags to filter runs and apply shared options | features-test-tags |
| Reporters | Built-in reporters, default selection, CI/output config | features-reporters |
| Benchmarking | Write benchmarks with the bench fixture (Tinybench) | features-benchmarking |
Advanced
| Topic | Description | Reference |
|---|---|---|
| Vi Utilities | vi helper: mock, spyOn, fake timers, hoisted, waitFor | advanced-vi |
| Environments | Test environments: node, jsdom, happy-dom, custom | advanced-environments |
| Type Testing | Type-level testing with expectTypeOf and assertType | advanced-type-testing |
| Projects | Multi-project workspaces, different configs per project | advanced-projects |
FAQ
What does the vitest skill do?
Vitest fast unit testing framework powered by Vite with Jest-compatible API. Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures.
How do I install vitest?
Run npx skills add https://github.com/onmax/nuxt-skills --skill vitest in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/vitest/ (personal) or .claude/skills/vitest/ (project).
Which AI agents can use vitest?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is vitest safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains vitest?
It is published by onmax in onmax/nuxt-skills. It has 3,139 recorded installs.
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