TypeError: Cannot read property 'createElement' of null

Question

I'm trying to click on a sidebar that has the following structure:

<div class=“sidebar”>
  <nav class=“subnav”>
    <ul>
      <li>
    <a class=“subnav-toggle”></a>
    <div>
      <ul>
        <li class=subnav-item>…</li>
        <li class=subnav-item>…</li>
        <li class=subnav-item>…</li>
      </ul>
    </div>
      </li>
      <li>…</li>
      <li>…</li>
      <li>…</li>
      <li>…</li>
    </ul>
  </nav>
</div>

and I created the following page model:

(Note: I want to get the higher level menu items on the navbar, not the second level <li>)

import { Selector } from 'testcafe';

export class PageModel {
  constructor () {
    this.firstItem = Selector('.subnav > ul > li').nth(0);
    this.secondItem = Selector('.subnav > ul > li').nth(1);
    ...
  }
}

finally, my test script is as follows:

import { PageModel } from 'myclass';

const a_item = new PageModel();
...
test ('Sample test', async t => {
  await t
    .hover(a_item.firstItem);
});

Testcafe successfuly hovers over the element I selected. However, I get an error saying that TypeError: Cannot read property 'createElement' of null.

How do I solve this issue?

** Update **

I updated my query based on a query that I put on the console.

document.querySelectorAll('.subnav > ul > li')
NodeList(8) [li, li, li, li, li, li, li, li]

Answer 1

With your selector,

Selector('subnav').find('li > a').nth(0);

you are selecting the first A that is the immediate child of a LI that is somewhere under "subnav".

I think what you actually want to do is find the li elements of the "outer" list, like this:

 Selector('.subnav > ul > li').nth(0);