vitest

Use vi.mock with a factory function, which is hoisted to the top of the file before imports. For partial mocks, spread the result of importOriginal and override specific exports. Use vi.doMock for non-hoisted dynamic mocking with await import.

Install @vitest/coverage-v8 or @vitest/coverage-istanbul, then run vitest run --coverage. Configure the provider, reporters, include/exclude patterns, and thresholds under the coverage key in vitest.config.ts.

Vitest provides a Jest-compatible API, so most test suites work as a drop-in replacement. It shares config, transformers, and plugins with your Vite app, and supports globals mode so describe, it, and expect work without imports.

Yes, set environment to jsdom or happy-dom in the 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 calls are hoisted above imports, so top-level variables are undefined inside the factory. Wrap shared values in vi.hoisted so they are initialized before the mock factory executes.

Filter by file path as a CLI argument, by test name with -t or --testNamePattern, or by tags with --tags. Use test.only to focus a single test, and vitest related to run tests importing specific source files.