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by Anthony Fuantfu/skills5.9k stars
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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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Use this Skill: https://skilld.dev/gh/antfu/skills/vitest

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SKILL.md

≈46 tokens always: the name and description. ≈832 when used: this file. ≈26k more on demand in 20 files.

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

Source: SKILL.md on GitHub

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    The skill provides comprehensive documentation and reference material for the Vitest testing framework. It covers configuration, CLI usage, mocking, coverage, and advanced features like type testing and benchmarking. No security issues were detected; the instructions follow standard development and testing practices.

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Provenance

Signed by skilld at d02c484. This ties the file your Agent reads to that commit on GitHub. It does not review the instructions.

Last checked against GitHub 2 days ago.

Activeupdated 4 days ago

Capability

Other metadata
metadata
{
  "author": "Anthony Fu",
  "version": "2026.9.25",
  "source": "Generated from https://github.com/vitest-dev/vitest, scripts located at https://github.com/antfu/skills"
}

Topics

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What it does

Vitest is a Jest-compatible unit testing framework powered by Vite, with native ESM, TypeScript, and JSX support. Use it for writing tests with smart watch mode, mocking, fixtures, coverage reporting, and snapshot testing in projects already using Vite.

Generated from the current SKILL.md.

Frequently asked

Is Vitest a drop-in replacement for Jest?
Mostly. Vitest provides a Jest-compatible API and can run most Jest test suites without modification, but it uses Vite's transformation pipeline instead of Jest's, so some edge cases may differ.
Does Vitest require configuration?
No. It natively supports ESM, TypeScript, and JSX out of the box and shares Vite's config, transformers, and resolvers, so many projects need minimal or no additional setup.
What coverage providers does Vitest support?
Vitest includes built-in coverage via V8 or Istanbul providers.
Can I run tests in parallel?
Yes. Vitest uses multi-threaded workers for parallel test execution and supports sharding across multiple processes.
What test environments are available?
Vitest supports node, jsdom, happy-dom, and custom environments.

Generated from the current SKILL.md. These answers refresh after source changes.