如何用 jest 测试 axios 拦截器

Question

在我的项目中，我有一个命名空间，用于导出一些使用 Axios 的函数，在同一个文件中，我向 axios 实例添加了一个拦截器，如下所示：

axios.interceptors.response.use(
    (res) => res,
    (error) => {
      if (
        error.response &&
        (error.response.status?.toString() === "400" ||
          error.response.status?.toString() === "403" ||
          error.response.status?.toString() === "404")
      ) {
        return Promise.reject(
          Error(JSON.stringify(error.response.data?.status?.errors[0]))
        );
      } else if (error.response) {
        return Promise.reject(
          Error(
            `server responsed with the following code: ${error.response?.status} and the following message: ${error.response?.statusText}`
          )
        );
      } else if (error.request) {
        return Promise.reject(
          Error(
            "The request was made but no response was received, check your network connection"
          )
        );
      } else Promise.reject(error);
    }
);

我想测试这个拦截器是否按预期工作，我在这里搜索表单并用谷歌搜索了很多，但所有答案基本上都是在嘲笑拦截器而不是测试它。

我试过了：

1. 模拟 axios 发布请求的响应并检查返回的 AxiosPromise，但它只包含我模拟的结果。当我使用mockResolvedValue 模拟时，它似乎忽略了拦截器。
2. 我尝试向模拟的 axios 实例添加一个拦截器，但这也不起作用。

谢谢

Answer 1

使用这个模拟功能

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

Answer 2

您必须模拟拦截器并运行回调。

下面是一个例子：

httpService.ts

import axios from "axios";
import { toast } from "react-toastify";

axios.interceptors.request.use((config) => {
  config.baseURL = process.env.API_URL || "http://localhost:5000";
  return config;
});

axios.interceptors.response.use(null, (error) => {
  const expectedError =
    error.response &&
    error.response.status >= 400 &&
    error.response.status < 500;

  if (!expectedError) {
    toast.error("An unexpected error occured");
  }

  return Promise.reject(error);
});

export default {
  get: axios.get,
  post: axios.post,
  put: axios.put,
  delete: axios.delete,
};

httpService.test.ts

import axios from "axios";
import { toast } from "react-toastify";
import "./httpService";

jest.mock("axios", () => ({
  __esModule: true,
  default: {
    interceptors: {
      request: { use: jest.fn(() => {}) },
      response: { use: jest.fn(() => {}) },
    },
  },
}));

const fakeError = {
  response: {
    status: undefined,
  },
};

const mockRequestCallback = (axios.interceptors.request.use as jest.Mock).mock
  .calls[0][0];
const mockResponseErrorCallback = (axios.interceptors.response.use as jest.Mock)
  .mock.calls[0][1];
const toastErrorSpy = jest.spyOn(toast, "error");

beforeEach(() => {
  toastErrorSpy.mockClear();
});

test("request error interceptor", () => {
  expect(mockRequestCallback({})).toStrictEqual({
    baseURL: "http://localhost:5000",
  });
});

test("unexpected error on response interceptor", () => {
  fakeError.response.status = 500;

  mockResponseErrorCallback(fakeError).catch(() => {});
  expect(toastErrorSpy).toHaveBeenCalled();
});

test("expected error on response interceptor", () => {
  fakeError.response.status = 400;

  mockResponseErrorCallback(fakeError).catch(() => {});
  expect(toastErrorSpy).not.toHaveBeenCalled();
});

Answer 3

不使用 axios 把函数拉出来测试一下怎么样？

import axios, { AxiosError, AxiosResponse } from 'axios'

export const onFullfilled = (response: AxiosResponse) => {
  // Your interceptor handling a successful response
}
export const onRejected = (error: AxiosError) => {
  // Your interceptor handling a failed response
}

axios.interceptors.response.use(onFullfilled, onRejected)

现在您可以测试函数 onFullfilled 和 onRejected，减少对 axios 的依赖。