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lbfeng
V2EX  ›  JavaScript

jest mock 返回 undefined

  •  
  •   lbfeng · 2021-02-17 22:56:26 +08:00 · 1325 次点击
    这是一个创建于 1134 天前的主题,其中的信息可能已经有所发展或是发生改变。

    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。

    4 条回复    2021-02-18 10:03:23 +08:00
    red2dog
        1
    red2dog  
       2021-02-17 23:10:28 +08:00
    jest.mock('./client',()=>{ return '你要 mock 的东西' }); 你 mock 啥都没传肯定是 undefined 啊
    lbfeng
        2
    lbfeng  
    OP
       2021-02-17 23:29:39 +08:00
    @red2dog 你说的官方文档里有,我试过了没用。
    lbfeng
        3
    lbfeng  
    OP
       2021-02-17 23:30:41 +08:00
    @red2dog Calling jest.mock() with the module factory parameter https://jestjs.io/docs/en/es6-class-mocks
    KuroNekoFan
        4
    KuroNekoFan  
       2021-02-18 10:03:23 +08:00
    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?
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