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.

Requirements: Vite >=v6.0.0, Node >=v20.0.0

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 via node:child_process (default) or node:worker_threads
Built-in coverage via V8 (default) or Istanbul
Snapshot testing, mocking, and spy utilities via Tinyspy
Browser mode for real browser component testing
Benchmarking via Tinybench
In-source testing
Type testing via expect-type
Sharding for CI parallelism

Based on Vitest 4.x (v4.0.17). Key v4 changes: workspace replaced with projects, pool options are top-level, V8 coverage uses AST-based analysis, coverage.all removed, basic reporter removed.

vitest