vitest

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 3.x, generated at 2026-01-28. ## 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) ...