anchor.diff:      }
   
       elements.classes = [];
  -    for (Element e in elements) {
  -      expect(e.classes, []);
  -    }
  -    document.documentElement.children.remove(listElement);
  +    expect(view(elements.classes), '[]');
  +    expect(view(elements), '[[], [], [], []]');
     });
   
     test('listMap', () {
       var elements = listElementSetup();
       expect(elements.classes.map((c) => c.toUpperCase()).toList(),
           unorderedEquals(['QUX', 'QUUX', 'META', 'CLASSY', 'LASSY']));
  -    document.documentElement.children.remove(listElement);
     });
   
     test('listContains', () {
       var elements = listElementSetup();
       expect(elements.classes.contains('lassy'), isTrue);
       expect(elements.classes.contains('foo'), isFalse);
  -    document.documentElement.children.remove(listElement);
     });
   
   
  
positive.code: 
    Element makeListElement() =>
      new Element.html('<ul class="foo bar baz">'
          '<li class="quux qux"><li class="meta">'
          '<li class="classy lassy"><li class="qux lassy"></ul>');
  
    Set<String> makeClassSet() => makeElementWithClasses().classes;
  
    Set<String> extractClasses(Element el) {
      final match = new RegExp('class="([^"]+)"').firstMatch(el.outerHtml);
      return new LinkedHashSet.from(match[1].split(' '));
    }
  
    test('affects the "class" attribute', () {
  
negative.code:     expect(classes, orderedEquals(['qux','bar', 'foo']));
    });
  
    test('retainAll', () {
      final classes = makeClassSet();
      classes.retainAll(['bar', 'baz', 'qux']);
      expect(classes, orderedEquals(['bar', 'baz']));
    });
  
    test('removeWhere', () {
      final classes = makeClassSet();
      classes.removeWhere((s) => s.startsWith('b'));
      expect(classes, orderedEquals(['foo']));
    });
  
    test('retainWhere', () {
      final classes = makeClassSet();
      classes.retainWhere((s) => s.startsWith('b'));
      expect(classes, orderedEquals(['bar', 'baz']));
    });
  
    test('containsAll', () {
      final classes = makeClassSet();
      expect(classes.containsAll(['foo', 'baz']), isTrue);
      expect(classes.containsAll(['foo', 'qux']), isFalse);
      expect(classes.containsAll(['foo', 'baz'].toSet()), isTrue);
      expect(classes.containsAll(['foo', 'qux'].toSet()), isFalse);
    });
  