如何在 Jest 中使用回调测试异步 function？

Question

I'm having a hard time finding info on how to test this function:

const MyService = {
  async stringify (entry, cb) {
    try {
      const response = await axios.post('localhost:3005/stringify', {
        entry
      })
      
      cb(null, response.data)

    } catch (minificationError) {

      if (minificationError.response.status === 500) {
        cb('error 1', null)
      } else {
        cb('error 2', null)
      }

    }
  }
}

I understand I can import axios and mock the .post like this:

axios.post.mockResolvedValue({
   data: { some: 'value' }
})

That'd work great if I the MyService was returning the promise... but how do I deal with the callback? Is this a bad practice and should the service be returning the promise and then handle errors in the component functions instead?

Additionally, how would I mock a status code with jest (to test the failed states?)

Answer 1

First, you have to set up mock axios after that you have to call your mockapi's in your test case

const axios = {
  post: jest.fn(() => {
    return Promise.resolve({
      data: {},
    });
  }),

  create: () => axios,
  request: {},
  defaults: {
    adapter: {},
    headers: {},
  },
  interceptors: {
    request: {
      use() {},
    },
    response: {
      use() {},
    },
  },
};

Once you setup mock axios then you can access in your test case and return whatever mock response and status code you want.

mockAxios.post.mockImplementation((url) => {
  if (url.includes("something")) {
    return Promise.resolve({ data:{"response":""}, status: 200 });
  } 
  return Promise.reject(new Error("not found"));
});