jest-mocking.js

// src/getHeadlines.js
export default () => {
  // do stuff
}

// __tests__/myTest.js
import getHeadlines from '../src/getHeadlines'
jest.mock('../src/getHeadlines', () => (user, type) => ({ // notice that the mocked function is the return of an initial function
  data: [user, type, 'misc']
})


// and here's a version if the function you want to mock isn't the default export

// src/getHeadlines.js
export const getHeadlines () => {
  // do stuff
}

// __tests__/myTest.js
import { getHeadlines } from '../src/getHeadlines'
jest.mock('../src/getHeadlines', () => ({ // here the return of the initial function is an object representing all the exports in the module
  getHeadlines: (user, type) => ({
    data: [user, type, 'misc']
  })
}))



it('should return headlines by type', async ()=>{
  const headlines = await getHeadlines('abc','xyz'); // your function is async so it should be treated as such in the test
  
  expect(headlines.data.length).toBe(3);
  
  expect(headlines.data[0]).toEqual('abc')
  expect(headlines.data[1]).toEqual('xyz')
  expect(headlines.data[2]).toEqual('misc')
})


// note if you wanted we could make the mocked `getHeadlines` async as well like this:

jest.mock('../src/getHeadlines', () => ({
  getHeadlines: async (user, type) => {
    await fakeDelay()
    return [user, type, 'misc']
  }
}))

const fakeDelay = () => new Promise((resolve, reject) => setTimeout(resolve, 10))