unit testing - Mocking dependency of module/function under test in Javascript -

let's want test following example:

import {fetchresourcefrombackend} './myfetch';  const fetchsomething = (dispatch) => {    dispatch(2);    return fetchresourcefrombackend('/api/abc').then( result => {     dispatch(3);   }); }; 

fetchresourcefrombackend complicated function. how can test this, , not affected fetchresourcefrombackend code (any pattern or tool recommendations, use mocha , sinon cannot achieve)?

is option provide fetchresourcefrombackend argument fetchsomething can mock it?

using jest @mikhail suggested solved this:

// test/something-test.js  import {myfetch} '../_mocks_/utilities';  jest.domock('modules/utilities', () =>({     myfetch: myfetch }));   const {fetchsomething} = require('modules/something');  describe('#fetchsomething', ... 

here fetchsomething function under test has internal dependency on myfetch function 'modules/utilities'. mock dependency myfetch '../_mocks_/utilities'.