没有连接到DB的服务的Jest测试

// userService.js
const db = require('./db');

async function getUserById(id) {
  return await db.query('SELECT * FROM users WHERE id = ?', [id]);
}

module.exports = { getUserById };

// userService.test.js
const { getUserById } = require('./userService');
const db = require('./db');

jest.mock('./db', () => ({
  query: jest.fn(() => Promise.resolve([{ id: 1, name: 'John Doe' }]))
}));

describe('getUserById', () => {
  it('should return user data', async () => {
    const user = await getUserById(1);
    expect(user).toEqual([{ id: 1, name: 'John Doe' }]);
    expect(db.query).toHaveBeenCalledWith('SELECT * FROM users WHERE id = ?', [1]);
  });
});

beforeEach(() => {
  db.query.mockClear();
});