vitest

Import test and expect from vitest, define tests with test() or it(), and group them with describe(). Vitest supports async tests, parameterized tests via test.each or test.for, and modifiers like skip, only, todo, and concurrent.

Use vi.fn() for mock functions, vi.spyOn() for object methods, and vi.mock() for module mocking, which is hoisted before imports. For dynamic imports use vi.doMock(), and use vi.hoisted() to reference variables inside mock factories.

Vitest provides a Jest-compatible API, so most Jest test suites work as drop-in replacements. It adds native ESM, TypeScript, and JSX support without configuration and shares config, transformers, and plugins with your Vite app.

Yes, Vitest has built-in coverage via the V8 or Istanbul providers, enabled with the --coverage flag or coverage.enabled in config. It supports text, json, html, and lcov reporters plus line, branch, function, and statement thresholds.

Set the test environment to jsdom or happy-dom in your config, or add a // @vitest-environment jsdom comment per file. For real browser testing, use Vitest Browser Mode with Playwright as the provider.

vi.mock is hoisted to the top of the file, so it cannot intercept imports that happen later at runtime. Use vi.doMock() before the dynamic import and vi.doUnmock() afterward to restore the original module.