An example of how I was using a sinon stub to mock creating uuids

create_stub_example.js

import uuid from 'node-uuid';
import sinon from 'sinon';
const mockId = '00000000-0000-0000-0000-000000000000';

describe('some test', () => {
  it('does something', () => {
    // create stub
    sinon.stub(uuid, 'v4', function () {
      return mockId;
    });
    expect(someFunction()).to.contain(mockId); // call some function that uses uuid.v4()
    uuid.v4.restore(); // this is important when using gulp.watch
  });
});