anchor.diff:      [TestStrategy strategy = const TestStrategy()]) {
     return strategy.testElements(resolvedAst1, resolvedAst2, 'element',
             resolvedAst1.element, resolvedAst2.element) &&
  -      // Compute AST equivalence by structural comparison.
  -      strategy.test(
  -          resolvedAst1,
  -          resolvedAst2,
  -          'node',
  -          resolvedAst1.node.toDebugString(),
  -          resolvedAst2.node.toDebugString()) &&
  +      new NodeEquivalenceVisitor(strategy).testNodes(resolvedAst1, resolvedAst2,
  +          'node', resolvedAst1.node, resolvedAst2.node) &&
         testTreeElementsEquivalence(resolvedAst1, resolvedAst2, strategy);
   }
   
  
positive.code:         elements2.getRedirectingTargetConstructor(node2));
    }
  }
  
negative.code: import '../tree/nodes.dart';
  import '../universe/selector.dart';
  import '../universe/use.dart';
  import '../util/util.dart';
  import 'resolved_ast_serialization.dart';
  
  /// Equality based equivalence function.
  