vitest

Generated source view for the actual executable engineering/vitest skill. The durable routing article is Browser Testing Skills. Source: skills/engineering/vitest/SKILL.md

Runtime Source

Bundled Resources

These files are part of the executable skill folder and must be preserved with the skill source.

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.

Skill Source

---
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: "2026.6.22"
  source: Generated from https://github.com/vitest-dev/vitest, scripts located at https://github.com/antfu/skills
origin: skills-sh
source_slug: "antfu/skills/vitest"
source_repo: "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.x (beta), generated at 2026-06-22.

## 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) |

---

Timeline

• 2026-07-15 | Generated a browseable source page from the actual executable skill file. Source: skills/engineering/vitest/SKILL.md