jest mock 返回 undefined

[lbfeng]

client.js

module.exports = class ProductsClient {
  async getById(id) {
    const url = `http://localhost:3000/api/products/{id}`;
    const response = await fetch(url);
    return await response.json();
  }
}

manager.js

const ProductsClient = require('./client');

module.exports = class ProductManager {
  async getProductToManage(id) {
    const productsClient = new ProductsClient();
    const productToManage = await productsClient.getById(id)
      .catch(err => alert(err));
    return productToManage;
  }
}

test.js

const ProductsClient = require('./client');
const ProductManager = require('./manager');

jest.mock('./client');

describe('test', () => {
  test('111', async () => {
    const expectedProduct = {
      id: 1,
      name: 'football',
    };
    const mockGetById = jest.fn();
    mockGetById.mockResolvedValue(expectedProduct);
    ProductsClient.prototype.getById = mockGetById;
    
  
    const productManager = new ProductManager();  
    const result = await productManager.getProductToManage(1); 
    expect(result.name).toBe('football');
  })
})

在 test.js 中 mock client 完全没问题。一旦把const productsClient = new ProductsClient();拿到class ProductManager外，getById就返回 undefined

const ProductsClient = require('./client');

const productsClient = new ProductsClient();

module.exports = class ProductManager {
  async getProductToManage(id) {
    const productToManage = await productsClient.getById(id) // undefined
      .catch(err => alert(err));
    return productToManage;
  }
}

jest mock module 文档里也没找到类似的例子。

[red2dog]

jest.mock('./client',()=>{ return '你要 mock 的东西' }); 你 mock 啥都没传肯定是 undefined 啊

[lbfeng]

@red2dog 你说的官方文档里有，我试过了没用。

[lbfeng]

@red2dog Calling jest.mock() with the module factory parameter https://jestjs.io/docs/en/es6-class-mocks

[KuroNekoFan]

云了一下
应该是你最后的写法里，实例化 ProductsClient 的时候，'./client'还没被 mock
试试把 jest.mock('./client');放到最顶？