vitest

Use vi.mock with a factory function, which is hoisted to the top of the file before imports run. For partial mocks, call importOriginal inside the factory and spread the actual module. 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 patterns, and thresholds under test.coverage in vitest.config.ts to enforce minimum line and branch percentages.

Vitest provides a Jest-compatible API, so most test files using describe, it, expect, and jest-style matchers work with minimal changes. Replace jest.mock with vi.mock and jest.fn with vi.fn, and reuse your Vite config for transforms and aliases.

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

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 during development, and vitest related to run tests importing specific source files.

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.