如何在TypeOrm中模拟EntityManager.transaction()测试？

import { createConnection, getConnection } from 'typeorm';
import { EntityManager } from 'typeorm/entity-manager/EntityManager';
import { ConnectionOptions } from 'typeorm/connection/ConnectionOptions';
import { User } from '../entities/User'; // 假设有一个User实体

describe('Transaction Test', () => {
  let connection: any;
  let entityManager: EntityManager;

  before(async () => {
    const connectionOptions: ConnectionOptions = {
      // 配置数据库连接选项
      type: 'mysql',
      host: 'localhost',
      port: 3306,
      username: 'root',
      password: 'password',
      database: 'test',
      entities: [User],
      synchronize: true,
    };

    connection = await createConnection(connectionOptions);
    entityManager = getConnection().manager;
  });

  after(async () => {
    await connection.close();
  });

  it('should rollback transaction on error', async () => {
    await entityManager.transaction(async (transactionalEntityManager) => {
      try {
        // 在事务中执行一些操作
        const user = new User();
        user.name = 'John Doe';
        await transactionalEntityManager.save(user);

        // 抛出一个错误，模拟事务失败
        throw new Error('Simulated error');
      } catch (error) {
        // 错误处理逻辑
        console.error(error);
      }
    });

    // 确保事务回滚成功
    const users = await entityManager.find(User);
    expect(users.length).toBe(0);
  });
});