Our review
Vitest is a Vite-powered unit testing framework with a Jest-compatible API, providing fast test execution, mocking, snapshots, coverage, and advanced features like type testing and test filtering.
Strengths
- Seamless Vite integration, reusing its config, transformers, and plugins
- Jest-compatible API eases migration from Jest
- Built-in mocking, coverage (V8 or Istanbul), and snapshot testing
- Smart watch mode and parallel execution via worker threads
Limitations
- Requires familiarity with the Vite ecosystem for advanced configuration
- Not fully compatible with all Jest plugins or custom transforms
- Advanced features like type testing may require extra setup in some environments
When you need a fast, modern unit testing setup for a Vite-based or TypeScript project with mocking and coverage support.
When you rely on a mature Jest plugin ecosystem or need to test non-Vite environments with heavy legacy dependencies.
Security analysis
SafeThe skill is purely informational documentation about the Vitest testing framework. It declares no allowed tools and contains no executable or destructive instructions. No risk of exfiltration, unsafe commands, or obfuscation.
No concerns found
Examples
Write a Vitest unit test for the `add` function in `src/utils.ts`, including edge cases and mocking a dependency.Run Vitest with coverage enabled for only test files matching 'user' and output an HTML report.Create a `vitest.config.ts` to test Vue components with jsdom and use `vi.mock` to stub an API module.name: vitest description: 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. metadata: author: Anthony Fu version: "2026.1.28" source: Generated from https://github.com/vitest-dev/vitest, scripts located at https://github.com/antfu/skills
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 |
TDD Red-Green-Refactor
Testing
Skill that guides Claude through the complete TDD cycle.
Web Accessibility Audit
Testing
Performs a comprehensive web accessibility audit following WCAG standards.
UAT Test Case Generator
Testing
Generates structured and comprehensive user acceptance test cases.