MSW used for HTTP mocking

setupServer with handlers

server.listen in beforeAll

onUnhandledRequest error

server.resetHandlers in afterEach

server.close in afterAll

server.use for error override

No direct HTTP client mock

HttpResponse.json used

Handlers in separate file

vi.useFakeTimers called

vi.useRealTimers in afterEach

vi.useFakeTimers in beforeEach

vi.advanceTimersByTime used

vi.runAllTimers or advanceTimersByTime for polling

vi.setSystemTime for date control

vi.fn() for callback tracking

Callback not called before delay

Multiple calls collapse to one

Expired token test uses time control

vi.mock for email module

vi.mock for promotions module

vi.importActual for partial mock

vi.spyOn on analytics

mockClear or mockReset in beforeEach

mockRestore for spies

toHaveBeenCalledWith assertion

rejects.toThrow for async errors

toEqual or toMatchObject for objects

vi.mock hoisting respected

sendWelcomeEmail mock resolved value