嘲笑笑话问题:“mockImplementation”不存在

我正在处理一个TypeScript项目,该项目使用DataLoader进行批量获取。我有一个名为getLoaders的函数,它返回一个具有不同实体类型的DataLoader实例的对象。

import DataLoader from 'dataloader';
import { EntityManager } from 'typeorm';
import { Address, batchEntitiesBy } from './somewhere';

export type LoadersType = ReturnType<typeof getLoaders>;

export function getLoaders(em: EntityManager) {
  return {
    addressById: new DataLoader<number, Address>((ids) =>
      batchEntitiesBy<Address, 'id'>(em, Address, 'id', ids)
    ),
    // Some other similar dataloaders
  };
}

在另一个文件中,我有一个名为processAddress的函数,它将其中一个loader对象作为参数。

export function processAddress(id: number, loaders: LoadersType): string {
  const Address = loaders.addressById.load(id);
  // Do something with Address
  return Address.name;
}

我想为processAddress编写Jest测试,在那里我可以为不同的测试用例模拟加载函数的不同实现。

以下是我的尝试:

  jest.mock('dataloader', () => {
    return jest.fn().mockImplementation(() => {
      return {
        load: jest.fn(),
        loadMany: jest.fn(),
        // ... any other methods you want to mock
      };
    });
  });

describe('processAddress', () => {
  const loadersMock = getLoaders({} as EntityManager);

  it('should call load with first mock', async () => {
    loadersMock.addressById.load.mockImplementation(() => Promise.resolve({ name: 'mocked value 1' }));
    
    const result = await processAddress(1, loadersMock);
    
    expect(loadersMock.addressById.load).toHaveBeenCalled();
    expect(loadersMock.addressById.load).toHaveBeenCalledWith(1);
    expect(result).toBe('mocked value 1');
  });

  it('should call load with second mock', async () => {
    loadersMock.addressById.load.mockImplementation(() => Promise.resolve({ name: 'mocked value 2' }));
    
    const result = await processAddress(2, loadersMock);
    
    expect(loadersMock.addressById.load).toHaveBeenCalled();
    expect(loadersMock.addressById.load).toHaveBeenCalledWith(2);
    expect(result).toBe('mocked value 2');
  });
});

在线

loadersMock.addressById.load.mockImplementation(() => ...

我得到了错误:

Property 'mockImplementation' does not exist on type

当我将其更改为

(loadersMock.addressById.load as jest.Mock)).mockImplementation(() => ...

我得到错误:

TypeError: loadersMock.addressById.load.mockImplementation is not a function