anchor.diff:  class SparkUIAccess {
     static SparkUIAccess _instance;
   
  -  static SparkUIAccess get instance {
  -    if (_instance == null) _instance = new SparkUIAccess();
  +  factory SparkUIAccess() {
  +    if (_instance == null) _instance = new SparkUIAccess._internal();
       return _instance;
     }
  +
  +  SparkUIAccess._internal();
   
     SparkPolymerUI get _ui => document.querySelector('#topUi');
     Element getUIElement(String selectors) => _ui.getShadowDomElement(selectors);
  
positive.code: }
  
  class SparkUITester {
    SparkUIAccess sparkAccess;
  
    SparkUITester(this.sparkAccess);
  
    Future openAndCloseWithX(MenuItemAccess menuItem) {
      DialogTester dialogTester = new DialogTester(menuItem.dialog);
  
negative.code:     }
    }
  
    SparkUIAccess get _sparkAccess => new SparkUIAccess();
  
    List<SparkMenuItem> get _menuItems => _sparkAccess.menu.querySelectorAll("spark-menu-item");
    SparkMenuItem _getMenuItem(String id) {
  