anchor.diff:  
   @reflectiveTest
   class NavigationTreeRendererTest extends NnbdMigrationTestBase {
  +  PathMapper pathMapper;
  +
     /// Render the navigation tree view for [files].
     Future<List<NavigationTreeNode>> renderNavigationTree(
         Map<String, String> files) async {
  
positive.code:     var aNode = response[0];
      expect(aNode.name, 'a.dart');
      expect(aNode.path, 'a.dart');
      expect(aNode.href, '/project/a.dart');
    }
  }
  
  
negative.code:           isNavigationTreeNode
                .named('a.dart')
                .havingPath(convertPath('lib/a.dart'))
                .havingHref('/project/lib/a.dart', pathMapper),
            isNavigationTreeNode
                .named('b.dart')
                .havingPath(convertPath('lib/b.dart'))
                .havingHref('/project/lib/b.dart', pathMapper)
          ]));
    }
  
  