testAddItemToDragList() {
    const item =
        dom.createDom(TagName.DIV, null, dom.createTextNode('newItem'));

    dlg.addItemToDragList(list, item);

    assertEquals(item, list.lastChild);
    assertEquals(4, dom.getChildren(list).length);

    events.listen(
        dlg, DragListGroup.EventType.BEFOREDRAGSTART, GoogEvent.preventDefault);

    testingEvents.fireMouseDownEvent(item);
    assertArrayEquals(
        'Should fire beforedragstart event when clicked',
        [
          DragListGroup.EventType.DRAGGERCREATED.toString(),
          DragListGroup.EventType.BEFOREDRAGSTART.toString(),
          DragListGroup.EventType.DRAGGERREMOVED.toString(),
        ],
        firedEventTypes);
  }
Tests that a new item can be added to a drag list after the control has
been initialized.
@suppress {checkTypes} suppression added to enable type checking