anchor.diff:    clearNodes(el) {
       throw 'not implemented';
     }
  -  appendChild(el, node) {
  -    throw 'not implemented';
  -  }
  +  appendChild(el, node) => null;
     removeChild(el, node) {
       throw 'not implemented';
     }
  -  remove(el) {
  -    throw 'not implemented';
  -  }
  -  insertBefore(el, node) {
  -    throw 'not implemented';
  -  }
  +  remove(el) => null;
  +  insertBefore(el, node) => null;
     insertAllBefore(el, nodes) {
       throw 'not implemented';
     }
  
positive.code:   getAttribute(element, String attribute) {
      throw 'not implemented';
    }
    setAttribute(element, String name, String value) {
      throw 'not implemented';
    }
    removeAttribute(element, String attribute) {
      throw 'not implemented';
    }
  
negative.code:   static void makeCurrent() {
      setRootDomAdapter(new Html5LibDomAdapter());
    }
  
    @override
    final attrToPropMap = const {
      'innerHtml': 'innerHtml',
      'readonly': 'readOnly',
      'tabindex': 'tabIndex',
    };
  
    Element parse(String templateHtml) => parser.parse(templateHtml).firstChild;
    query(selector) {
  