How do I install the Vitest skill?

Run npx skillmds@latest add ehyland/vitest in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Vitest safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Vitest?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Vitest free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Vitest?

ehyland (@ehyland) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Vitest by ehyland — Agent Skill

Name: Vitest
Author: ehyland

File contents

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 3.x, generated at 2026-01-28.

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

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

---name: vitestdescription: 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.---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 3.x, generated at 2026-01-28.## Core| Topic | Description | Reference || ------------- | --------------------------------------------------------------- | ---------------------------------------------- || Configuration | Vitest and Vite config integration, defineConfig usage | [core-config](./references/core-config.md) || CLI | Command line interface, commands and options | [core-cli](./references/core-cli.md) || Test API | test/it function, modifiers like skip, only, concurrent | [core-test-api](./references/core-test-api.md) || Describe API | describe/suite for grouping tests and nested suites | [core-describe](./references/core-describe.md) || Expect API | Assertions with toBe, toEqual, matchers and asymmetric matchers | [core-expect](./references/core-expect.md) || Hooks | beforeEach, afterEach, beforeAll, afterAll, aroundEach | [core-hooks](./references/core-hooks.md) |## Features| Topic | Description | Reference || ------------ | -------------------------------------------------------------- | ------------------------------------------------------------ || Mocking | Mock functions, modules, timers, dates with vi utilities | [features-mocking](./references/features-mocking.md) || Snapshots | Snapshot testing with toMatchSnapshot and inline snapshots | [features-snapshots](./references/features-snapshots.md) || Coverage | Code coverage with V8 or Istanbul providers | [features-coverage](./references/features-coverage.md) || Test Context | Test fixtures, context.expect, test.extend for custom fixtures | [features-context](./references/features-context.md) || Concurrency | Concurrent tests, parallel execution, sharding | [features-concurrency](./references/features-concurrency.md) || Filtering | Filter tests by name, file patterns, tags | [features-filtering](./references/features-filtering.md) |## Advanced| Topic | Description | Reference || ------------ | ------------------------------------------------------- | -------------------------------------------------------------- || Vi Utilities | vi helper: mock, spyOn, fake timers, hoisted, waitFor | [advanced-vi](./references/advanced-vi.md) || Environments | Test environments: node, jsdom, happy-dom, custom | [advanced-environments](./references/advanced-environments.md) || Type Testing | Type-level testing with expectTypeOf and assertType | [advanced-type-testing](./references/advanced-type-testing.md) || Projects | Multi-project workspaces, different configs per project | [advanced-projects](./references/advanced-projects.md) |

Frequently asked questions

Vitest