Vitest
Anthony FuCommunityCreated by Anthony Fu
- Skill
- Tool integration
- Software development
- MIT
- No issues found
AutoGineer summary
Written by AutoGineer from the skill’s own files, not by the author
Vitest is a testing framework built for the Vite ecosystem. It provides a Jest-compatible API and supports ESM, TypeScript, and JSX by default. It shares configuration, transformers, and plugins with Vite applications, allowing for integrated testing workflows. The framework includes features for mocking, snapshot testing, code coverage, and multi-threaded test execution.
What it does
- Provides a Jest-compatible API for writing and running unit tests
- Supports native ESM, TypeScript, and JSX without additional configuration
- Enables mocking of functions, modules, timers, and dates
- Offers built-in code coverage reporting using V8 or Istanbul
- Supports multi-project workspaces and varied test environments like Node, jsdom, and happy-dom
- Includes utilities for snapshot testing, test filtering, and benchmarking
When to use it
- When you need a testing framework that integrates directly with your Vite configuration
- When migrating existing test suites that rely on Jest-compatible APIs
- When you require specific test environments like jsdom or happy-dom for DOM-related testing
- When managing complex test setups across monorepos or multiple projects
Advantages
- Shares configuration and plugins with Vite projects
- Supports parallel test execution via multi-threaded workers
- Provides flexible test environment configuration per file or project
- Includes built-in support for snapshot testing and mocking utilities
Usage examples
- “How do I configure Vitest to use the jsdom environment for my tests?”
- The agent provides the vitest.config.ts configuration snippet using the environment: 'jsdom' property and explains how to install the necessary jsdom package.
- “Can I run different test configurations in the same Vitest process?”
- The agent explains how to use the projects field in the vitest.config.ts file to define multiple test suites with different environments or include patterns.
Install
Download the skill as a ZIP:
https://autogineer.com/agent-skills/antfu/vitest/downloadUnzip it into the cross-client skills folder of your project:
mkdir -p .agents/skills && unzip vitest.zip -d .agents/skills
Documentation by Anthony Fu
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 |
| 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 |
Files
- ATTRIBUTION.mdAdded by AutoGineer895 B
- GENERATION.md136 B
- LICENSELicence file added by AutoGineer1.1 KiB
- SKILL.md3.6 KiB
- references/advanced-environments.md4.9 KiB
- references/advanced-projects.md7.4 KiB
- references/advanced-type-testing.md4.6 KiB
- references/advanced-vi.md5.8 KiB
- references/core-cli.md4.9 KiB
- references/core-config.md7.7 KiB
- references/core-describe.md3.5 KiB
- references/core-expect.md8.8 KiB
- references/core-hooks.md4.8 KiB
- references/core-test-api.md5.5 KiB
- references/features-benchmarking.md3.9 KiB
- references/features-concurrency.md4.7 KiB
- references/features-context.md5.3 KiB
- references/features-coverage.md5.0 KiB
- references/features-filtering.md4.8 KiB
- references/features-mocking.md9.8 KiB
- references/features-reporters.md4.0 KiB
- references/features-snapshots.md5.2 KiB
- references/features-test-tags.md3.6 KiB
references/core-cli.md
name: vitest-cli description: Command line interface commands and options
Command Line Interface
Commands
vitest
Start Vitest in watch mode (dev) or run mode (CI):
vitest # Watch mode in dev, run mode in CI
vitest foobar # Run tests containing "foobar" in path
vitest basic/foo.test.ts:10 # Run specific test by file and line numbervitest run
Run tests once without watch mode:
vitest run
vitest run --coveragevitest watch
Explicitly start watch mode:
vitest watchvitest related
Run tests that import specific files (useful with lint-staged):
vitest related src/index.ts src/utils.ts --runvitest bench
Run only benchmark tests:
vitest benchvitest list
List all matching tests without running them:
vitest list # List test names
vitest list --json # Output as JSON
vitest list --filesOnly # List only test filesv5:
listparses test files statically instead of running them. Pass--no-static-parseto run them; tune with--static-parse-concurrency.
vitest doctor (v5)
Run the suite under alternative configs and recommend faster options (e.g. a different pool, isolate: false, fsModuleCache, lower maxWorkers). Needs a passing baseline; takes several times a normal run:
vitest doctorvitest init
Initialize project setup:
vitest init browser # Set up browser testingvitest --list-tags
List tags defined in config without running tests:
vitest --list-tags # Human-readable list
vitest --list-tags=json # JSON outputCommon Options
# Configuration
--config <path> # Path to config file
--project, -p <name> # Run specific project (v5 adds the -p shorthand)
# Filtering
--testNamePattern, -t # Run tests matching pattern
--tagsFilter <expr> # Run tests by tag expression, e.g. "db && !flaky"
--changed # Run tests for changed files
--changed HEAD~1 # Tests for last commit changes
--since-last-run # (5.1, experimental) Tests whose loaded files changed since their last run
--last-failed # (5.1) Only tests that failed in the last run (from results cache)
--dir <path> # Limit test discovery to a directory
# Reporters
--reporter <name> # default, verbose, tree, dot, json, html, junit, minimal, blob
--reporter=json --outputFile=report.json
# Coverage
--coverage # Enable coverage
--coverage.provider v8 # Use v8 provider
--coverage.reporter text,html
# Execution
--shard <index>/<count> # Split tests across machines
--bail <n> # Stop after n failures
--retry <n> # Retry failed tests n times
--repeats <n> # v5: repeat every test n times (hunt flaky tests)
--shuffle # Randomize test order
--no-file-parallelism # Run test files one at a time
# Watch mode
--no-watch # Disable watch mode
--standalone # Start without running (v4: runs matched files if a filter is passed)
# Environment
--environment <env> # jsdom, happy-dom, node
--globals # Enable global APIs
# Debugging
--inspect # Enable Node inspector
--inspect-brk # Break on start
# Output
--silent # Suppress console output
--no-color # Disable colorsPackage.json Scripts
{
"scripts": {
"test": "vitest",
"test:run": "vitest run",
"test:ui": "vitest --ui",
"coverage": "vitest run --coverage"
}
}Sharding for CI
Split tests across multiple machines. The blob reporter writes to .vitest/blob/ by default:
# Machine 1
vitest run --shard=1/3 --reporter=blob --outputFile=reports/blob-1.json
# Machine 2
vitest run --shard=2/3 --reporter=blob --outputFile=reports/blob-2.json
# Merge all blobs into a final report
vitest --merge-reports=reports --reporter=junit --reporter=defaultWatch Mode Keyboard Shortcuts
In watch mode, press:
a- Run all testsf- Run only failed testsu- Update snapshotsp- Filter by filename patternt- Filter by test name patternq- Quit
Key Points
Watch mode is default in dev, run mode in CI (when
process.env.CIis set)Use
--runflag to ensure single run (important for lint-staged)Both camelCase (
--testTimeout) and kebab-case (--test-timeout) workBoolean options can be negated with
--no-prefixFilter tests by tag with
--tagsFilter(tags must be declared in config) — see features-test-tags--merge-reportsand--reporter=blobdo not work in watch mode (--merge-reportsnow handles non-sharded multi-environment runs)v5: use
-pas shorthand for--project;vitest doctorsuggests faster config
<!-- Source references: - https://vitest.dev/guide/cli.html -->
Requirements and compatibility
Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta
“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.
Needs: Needs Node.js
Security
No issues found by our static scan· No issues found
A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.
Attribution and licence
- Created by
- Anthony Fu
- Publisher
- Anthony Fu (Community)
- Source
- antfu/skills · skills/vitest · commit f63e9ec
- Licence
- MIT License (redistribution allowed)
- LICENSE (added by AutoGineer from LICENSE.md)
- ATTRIBUTION.md (written by AutoGineer)
- Synced
AutoGineer is not affiliated with or endorsed by Anthony Fu or Anthony Fu.
Download ZIP
The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download vitest.zip