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 jsdom as a dev dependency and set environment: 'jsdom' in the test section of vitest.config.ts. Alternatively, add a // @vitest-environment jsdom comment at the top of individual test files. happy-dom is a faster alternative with fewer APIs.

Vitest provides a Jest-compatible API, so most test suites work as drop-in replacements. Replace jest.fn and jest.mock with vi.fn and vi.mock from 'vitest', and move configuration from jest.config into the test property of vitest.config.ts.

Pass a filename pattern as a CLI argument, use -t or --testNamePattern to filter by test name, or add test.only in the file. You can also use --changed for tests affected by git changes and --project to run a specific workspace project.

vi.mock calls are hoisted above imports, so top-level variables are not yet defined when the factory registers. Wrap shared values in vi.hoisted to create them before the mock factory executes, then reference them inside vi.mock.

Yes, configure coverage.thresholds in vitest.config.ts with minimum percentages for lines, functions, branches, and statements. Install @vitest/coverage-v8 for the default fast provider or @vitest/coverage-istanbul for broader compatibility, then run vitest run --coverage.