vitest▌

Expert knowledge for testing JavaScript/TypeScript projects using Vitest - a blazingly fast testing framework powered by Vite.

This skill helps you write effective tests using Vitest and React Testing Library following project conventions.

Detect the project type, generate the right Vitest configuration, and produce working test infrastructure. Not a reference card — this skill creates files.

Supported platforms:

vitest-testing

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.

Modern TypeScript testing with Vite-native speed, ESM-first design, and instant HMR feedback. \n \n Vite-powered test execution delivers 10-100x faster performance than Jest through HMR-based test running and native ES module support \n Built-in TypeScript support requires zero configuration; includes Jest-compatible API for straightforward migration from existing test suites \n Supports React and Vue component testing via Testing Library and Vue Test Utils, with jsdom/happy-dom environment opti

44 Vitest best practices rules organized by priority, covering async patterns, test setup, mocking, performance, snapshots, and assertions. \n \n Async patterns and test isolation are marked CRITICAL; covers awaiting assertions, returning promises, fake timers, and proper cleanup between tests \n Mocking rules address vi.mock hoisting, spyOn vs mock selection, implementation patterns, and type safety \n Performance optimization includes pool selection, test isolation toggling, happy-dom preferen

Vite-native unit and integration testing framework with Jest-compatible API and parallel execution. \n \n Supports testing Vue, React, and Svelte components with configurable environments (Node, jsdom, or browser mode) \n Provides Jest-compatible API including describe/it blocks, hooks, fixtures, and globals configuration \n Includes comprehensive mocking capabilities: vi.fn for function mocks, vi.mock for module mocking, and timer/date utilities \n Offers code coverage thresholds, snapshot test

Vite-powered unit testing framework with Jest-compatible API and native ESM support. \n \n Jest-compatible test syntax (test/describe/expect) with drop-in replacement capability for most Jest suites \n Native support for ESM, TypeScript, and JSX without additional configuration; shares Vite's transformation pipeline \n Smart watch mode reruns only affected tests based on module graph; multi-threaded workers enable parallel execution \n Built-in mocking (functions, modules, timers), snapshot test