jest.mock is not a function in react?

Question

Could you please tell me how to test componentDidMount function using enzyme .I am fetching data from the server in componentDidMount which work perfectly.Now I want to test this function.

here is my code https://codesandbox.io/s/oq7kwzrnj5

  componentDidMount(){
        axios
          .get('https://*******/getlist')
          .then(res => {
            this.setState({
              items : res.data.data
            })
          })
          .catch(err => console.log(err))
      }

I try like this

 it("check ajax call", () => {
      const componentDidMountSpy = jest.spyOn(List.prototype, 'componentDidMount');

      const wrapper = shallow(<List />);
    });

see updated code

https://codesandbox.io/s/oq7kwzrnj5

it("check ajax call", () => {
      jest.mock('axios', () => {
        const exampleArticles:any = {
          data :{
            data:['A','B','c']
          }
        }
        return {
          get: jest.fn(() => Promise.resolve(exampleArticles)),
        };
      });


    expect(axios.get).toHaveBeenCalled();
    });

error

Answer 1

You look like you're almost there. Just add the expect() :

expect(componentDidMountSpy).toHaveBeenCalled();

If you need to check if it was called multiple times, you can use toHaveBeenCalledTimes(count) .

Also, be sure to mockRestore() the mock at the end to make it unmocked for other tests.

List.prototype.componentDidMount.restore();

---

To mock axios (or any node_modules package), create a folder named __mocks__ in the same directory as node_modules , like:

 --- project root
  |-- node_modules
  |-- __mocks__

Inside of there, make a file named <package_name>.js (so axios.js ).

Inside of there, you'll create your mocked version.

If you just need to mock .get() , it can be as simple as:

export default { get: jest.fn() }

Then in your code, near the top (after import s), add:

import axios from 'axios';

jest.mock('axios');

In your test, add a call to axios.get.mockImplementation() to specify what it'll return:

axios.get.mockImplementation(() => Promise.resolve({ data: { data: [1, 2, 3] } });

This will then make axios.get() return whatever you gave it (in this case, a Promise that resolves to that object).

You can then do whatever tests you need to do.

Finally, end the test with:

axios.get.mockReset();

to reset it to it's default mocked implementation.