Sinon to mock a fetch call

import sinonStubPromise from 'sinon-stub-promise';
import sinon from 'sinon'
sinonStubPromise(sinon)


let stubedFetch = sinon.stub(window, 'fetch') )

window.fetch.returns(Promise.resolve(mockApiResponse()));

function mockApiResponse(body = {}) {
    return new window.Response(JSON.stringify(body), {
       status: 200,
       headers: { 'Content-type': 'application/json' }
    });
}