vitest_runner

Import describe, it, and expect from vitest, then group assertions inside describe blocks. Use expect with matchers like toBe for primitives, toEqual for objects, and toThrow for error cases.

Use vi.mock('./module', factory) to replace an entire module's exports, and vi.fn() to create standalone mock functions. Verify calls with matchers like toHaveBeenCalledWith, and reset state between tests with vi.clearAllMocks().

Vitest offers a Jest-compatible API while integrating natively with Vite configuration, so test settings stay synchronized with your build. It is the natural choice for Vite-based projects, while Jest remains common in older setups.

Yes, Vitest works with @testing-library/react to render components and @testing-library/user-event to simulate interactions. Configure the jsdom or happy-dom environment in vitest.config.ts for DOM-based tests.

Enable coverage by selecting the v8 or istanbul provider in your Vitest configuration and running tests with the coverage flag. The generated report shows which lines and branches your tests exercise.

Async tests fail silently when promises are not awaited. Always await expect(promise).rejects.toThrow() for rejections and await async calls inside it blocks so assertions run after resolution.