vitest

Vite-powered unit testing framework with Jest-compatible API and native ESM support. 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: The skill is based on Vitest 3.x, generated at 2026-01-28. - Shares Vite's config, transformers, and plugins; supports TypeScript, JSX, and ESM without extra setup - Smart watch mode reruns only affected tests based on module graph; multi-threaded workers enable parallel execution - Comprehensive testing utilities: test/describe/expect API, mocking (functions, modules, timers), snapshots, and fixtures - Built-in code coverage via V8 or Istanbul; test filtering by name, file patterns, and tags - Advanced features include type-level testing, custom environments (node, jsdom, happy-dom), and multi-project workspaces - 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