使用 jest.mock('axios') 时如何模拟拦截器？

Question

使用 jest 运行测试时，我有基本的测试套装语法：

jest.mock('axios');

describe('app', () => {
    let render

    beforeEach(() => {
        axiosMock.get.mockResolvedValueOnce({
            data: {greeting: 'hello there'},
        }),
        render= renderApp()
    });

    test('should render something', () => {
        expect(something).toBeInTheDocument();
    });


});

问题是我的代码中有拦截器，当使用 jest 命令输出运行测试时：

TypeError：无法读取未定义的属性“拦截器”

并指向拦截器对象

axiosInstance.interceptors.request.use(...

axiosInstance是存储axios.create返回的变量

export const axiosInstance = axios.create({...

在 SO How do I test axios in jest 上引用了这个 axios 线程，但它不涉及任何拦截器，所以并没有真正的帮助。

Answer 1

到此为止，简单明了jest.fn()

jest.mock('axios', () => {
    return {
        interceptors: {
            request: { use: jest.fn(), eject: jest.fn() },
            response: { use: jest.fn(), eject: jest.fn() },
        },
    };
});

Answer 2

确保模拟出拦截器和axios.create（如果使用）：

// Replace any instances with the mocked instance (a new mock could be used here instead):
axios.create.mockImplementation((config) => axios);

// Mock out the interceptor (assuming there is only one):
let requestCallback = () => {
  console.log("There were no interceptors");
};
axios.interceptors.request.use.mockImplementation((callback) => {
  requestCallback = callback;
});

// Mock out the get request so that it returns the mocked data but also calls the 
// interceptor code:
axios.get.mockImplementation(() => {
  requestCallback();
  return {
    data: "this is some data"
  };
});

注意如果这不起作用：

此示例假定创建和拦截器调用位于 Jest 可以模拟它们的位置。将axios.create 或axiosInstance.interceptors.request.use 行放在函数范围之外可能会导致上述模拟失败。这是 Jest 可以模拟出来的示例文件：

const axios = require('axios');

const DEBUG = true;

const customRequest = (url) => {
  // Example of axios.create from https://www.npmjs.com/package/axios#axioscreateconfig
  const axiosInstance = axios.create({
    baseURL: 'https://some-domain.com/api/',
    timeout: 1000,
    headers: {'X-Custom-Header': 'foobar'}
  });

  // Example of interceptor taken from https://stackoverflow.com/a/52737325/7470360:
  axiosInstance.interceptors.request.use((config) => {
    if (DEBUG) { console.info("Request called", config); }
    return config;
  }, (error) => {
    if (DEBUG) { console.error("Request error ", error); }
    return Promise.reject(error);
  });

  return axiosInstance.get(url);
}

module.exports = customRequest;

模拟代码将模拟出axios.create 调用和customRequest 中的axiosInstance 调用。将创建或拦截移到函数外都会导致模拟失败。

Answer 3

这是我嘲笑axios.create 及其interceptors 的方式：

jest.mock('axios', () => {
  return {
    create: () => {
      return {
        interceptors: {
          request: {eject: jest.fn(), use: jest.fn()},
          response: {eject: jest.fn(), use: jest.fn()},
        },
      };
    },
  };
});

之后我可以在我的测试代码中调用以下代码：

const client = axios.create({
  baseURL: 'http://some-url.com',
});

client.interceptors.request.use(config => {
  // some other test code
  return config;
});