vitest

Use when the user asks about Vitest mocking, spies, stubs, fake timers, config, or test runner behavior. Triggers on questions like "vi.fn", "vi.spyOn", "vi.mocked", "Mocked<T>", "mockResolvedValue", "restoreMocks", "vitest mock", "createMockInstance", "useFakeTimers", or how to accomplish test double patterns with Vitest.