How to test the content inside of a react-bootstrap <Modal>

test.js

import { mount, ReactWrapper } from 'enzyme';
import { Modal } from 'react-bootstrap';

// The Enzyme selector query will not work because the actual inside HTML of the modal lives else where in the DOM
// via portals. See: https://react-bootstrap.github.io/react-overlays/#portals
function getWrapperForModalPortal(parentWrapper) {
  // The Modal instance provides a reference to HTML content:
  // [1] https://github.com/react-bootstrap/react-bootstrap/blob/dddb9b966c7f3e79495be5c5730f7cce04813aaf/src/Modal.js#L228
  // [2] https://github.com/react-bootstrap/react-bootstrap/blob/419051127d913bbb149e81ed221500108ba0d7f3/test/ModalSpec.js#L32
  const modalInstance = parentWrapper.find(Modal).getNode()._modal.getDialogElement();
  return new ReactWrapper(modalInstance, modalInstance);
}

describe('Modal', () => {
  it('', () => {
    const modal = wrapper(<div>
        <Modal show>
          <div className="TestClassName">example</div>
        </Modal>
      </div>
    );  
    
    const modalWrapper = getWrapperForModalPortal(wrapper);
    const testDiv = modalWrapper.find('div').get(0);
    
    expect(testDiv.className).toEqual('TestClassName');
  });
});