/vitest

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: "2026.10.23"
  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 5.1.0-beta.1, generated at 2026-10-23.

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) | | Test Tags | Label tests with tags to filter runs and apply shared options | [features-test-tags](references/features-test-tags.md) | | Reporters | Built-in reporters, default selection, CI/output config | [features-reporters](references/features-reporters.md) | | Benchmarking | Write benchmarks with the bench fixture (Tinybench) | [features-benchmarking](references/features-benchmarking.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) |