Modules और API Calls की Mocking

jest.mock('./api');
import { fetchUser } from './api';

(fetchUser as jest.Mock).mockResolvedValue({ id: 1, name: 'Alice' });

test('renders user name', async () => {
  render(<Profile userId="1" />);
  await screen.findByText('Alice');
  expect(fetchUser).toHaveBeenCalledWith('1');
});

const onSubmit = jest.fn();
render(<Form onSubmit={onSubmit} />);

await user.click(screen.getByRole('button', { name: /submit/i }));

expect(onSubmit).toHaveBeenCalledOnce();
expect(onSubmit).toHaveBeenCalledWith({ email: 'alice@example.com' });

beforeEach(() => {
  jest.clearAllMocks(); // reset call counts and implementations
});

afterAll(() => {
  jest.restoreAllMocks(); // restore original implementations
});

import { setupServer } from 'msw/node';
import { http, HttpResponse } from 'msw';

const server = setupServer(
  http.get('/api/users', () => {
    return HttpResponse.json([{ id: 1, name: 'Alice' }]);
  })
);

beforeAll(() => server.listen());
afterEach(() => server.resetHandlers());
afterAll(() => server.close());

test('handles server error', async () => {
  server.use(
    http.get('/api/users', () => new HttpResponse(null, { status: 500 }))
  );

  render(<UserList />);
  await screen.findByText(/server error/i);
});

beforeEach(() => {
  const store: Record<string, string> = {};
  jest.spyOn(Storage.prototype, 'getItem').mockImplementation((key) => store[key] ?? null);
  jest.spyOn(Storage.prototype, 'setItem').mockImplementation((key, val) => { store[key] = val; });
});

jest.useFakeTimers();

test('shows toast for 3 seconds', () => {
  render(<Toast message="Saved!" />);
  expect(screen.getByText('Saved!')).toBeInTheDocument();

  jest.advanceTimersByTime(3000);
  expect(screen.queryByText('Saved!')).not.toBeInTheDocument();
});

afterEach(() => jest.useRealTimers());

jest.mock('./services/auth', () => ({
  login: jest.fn().mockResolvedValue({ token: 'test-token' }),
  logout: jest.fn()
}));