anchor.diff:  
   bool _idMatcher(int a, int b) => a == b;
   int _idMapper(int a) => a;
  -
  -const _luggage = const [1,2,3,4,5];
  
positive.code: // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  library test.nv.shared.mapped_list_view;
  
  import 'dart:async';
  import 'package:observe/observe.dart';
  import 'package:nv/src/shared.dart';
  import 'package:unittest/unittest.dart';
  
negative.code: import 'test_collection_view.dart' as test_cv;
  
  void main() {
    group('identity', () {
      group('wrapping ReadOnlyObservableList', () {
        test_rool.sharedMain(_simpleFactory);
      });
      group('wrapping CollectionView', () {
        test_cv.sharedMain(_simpleFactory);
      });
    });
  }
  
  ObservableList<int> _simpleFactory(ObservableList<int> source) {
  