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I have the following method in a class:

import axios from 'axios'

public async getData() {
   const resp = await axios.get(Endpoints.DATA.URL)
   return resp.data
}

Then I am trying to set up a Jest test that does this:

jest.mock('axios')

it('make api call to get data', () => {
   component.getData()
   expect(axios.get).toHaveBeenCalledWith(Endpoints.DATA.URL)
})

The problem is that because I am not mocking the return value, then it gives an error for resp.data because I'm calling data on null or undefined object. I spent at least 2 hours trying various ways to get this working but I can't find a way such that I can mock axios.get with some return value.

Jest's documentation uses JavaScript so they give this example axios.get.mockResolvedValue(resp) but I can't call mockResolvedValue because that method does not exist on axios.get in TypeScript.

Also, if you know other good testing library for React other than Jest that does this stuff easily for TypeScript, feel free to share.

Answers

In start of file:

import axios from 'axios';
jest.mock('axios');
const mockedAxios = axios as jest.Mocked<typeof axios>;

Now you can use it as usual mock:

mockedAxios.get.mockRejectedValue('Network error: Something went wrong');
mockedAxios.get.mockResolvedValue({ data: {} });