React, jest: can't access parentNode with ref

I am learning how to test components.

This is the component I'm trying to add tests to: https://github.com/sickdyd/react-dynamic-badge/tree/testing

This is the main file for the tests: https://github.com/sickdyd/react-dynamic-badge/blob/testing/src/test/test/DynamicBadge.test.js

My component functionality depends on its parent element width. In particular it uses this function:

function getElementContentWidth(element) {

  let styles = window.getComputedStyle(element);
  let padding = parseFloat(styles.paddingLeft) + parseFloat(styles.paddingRight);

  return element.clientWidth - padding;
}

Which is called as follows in React.useLayoutEffect():

const containerW = getElementContentWidth( refContainer.current.parentNode );

Where refContainer is a div that wraps my component in the component render:

return <div data-testid="badge" ref={refContainer}>{ output }</div>

This is my test():

test("matches snapshot", ()=> {

  // I found this here: https://reactjs.org/docs/test-renderer.html#ideas
  // but I'm not really sure what this is doing...    
  function createNodeMock(element) {

    if (element.type === 'div') {
      return {
        focus() {},
      };
    }
    return <div></div>;
  }

  const options = { createNodeMock };

  Object.defineProperty(window, 'getComputedStyle', { 
    value: () => ({
        getPropertyValue: (prop) => {
            return '';
        }
    })
  });

  const tree = renderer.create(

    <div style=>
      <DynamicBadge
        items={[
          "Item 1",
          "Item 2",
          "Item 3",
        ]}
      />
    </div>

    , options

    ).toJSON();

    expect(tree).toMatchSnapshot();
});

The test fails at: return element.clientWidth - padding; saying TypeError: Cannot read property 'clientWidth' of undefined.

How can I make it work?