testGetLength() {
    const parentNode = googDom.createElement(TagName.P);

    assertEquals(
        'Length 0 and no children', 0, editorNode.getLength(parentNode));

    const childNode1 = document.createTextNode('node 1');
    const childNode2 = document.createTextNode('node number 2');
    const childNode3 = document.createTextNode('');
    parentNode.appendChild(childNode1);
    parentNode.appendChild(childNode2);
    parentNode.appendChild(childNode3);
    assertEquals(
        'Length 0 and 3 children', 3, editorNode.getLength(parentNode));
    assertEquals('Text node, length 6', 6, editorNode.getLength(childNode1));
    assertEquals('Text node, length 0', 0, editorNode.getLength(childNode3));
  }
Test that getLength returns 0 if the node has no length and no children,
the # of children if the node has no length but does have children,
and the length of the node if the node does have length