在javascript中使用jest模拟类方法

// DatabaseService.js
class DatabaseService {
  fetchData() {
    // 实际的数据获取逻辑
  }
}

module.exports = DatabaseService;

// UserService.js
const DatabaseService = require('./DatabaseService');

class UserService {
  constructor() {
    this.dbService = new DatabaseService();
  }

  getUser(id) {
    return this.dbService.fetchData(id);
  }
}

module.exports = UserService;

// UserService.test.js
const DatabaseService = require('./DatabaseService');
const UserService = require('./UserService');

jest.mock('./DatabaseService');

describe('UserService', () => {
  let userService;

  beforeEach(() => {
    userService = new UserService();
  });

  it('should fetch user data', async () => {
    const mockData = { id: 1, name: 'John Doe' };
    DatabaseService.prototype.fetchData.mockResolvedValue(mockData);

    const user = await userService.getUser(1);

    expect(user).toEqual(mockData);
    expect(DatabaseService.prototype.fetchData).toHaveBeenCalledWith(1);
  });
});