anchor.diff:  
     @override
     void reset() {
  -    analysisContext2 = AnalysisContextFactory.oldContextWithCore();
  +    if (AnalysisEngine.instance.useTaskModel) {
  +      analysisContext2 = AnalysisContextFactory.contextWithCore();
  +    } else {
  +      analysisContext2 = AnalysisContextFactory.oldContextWithCore();
  +    }
     }
   
     @override
     void resetWithOptions(AnalysisOptions options) {
  -    analysisContext2 =
  -        AnalysisContextFactory.oldContextWithCoreAndOptions(options);
  +    if (AnalysisEngine.instance.useTaskModel) {
  +      analysisContext2 =
  +                AnalysisContextFactory.contextWithCoreAndOptions(options);
  +    } else {
  +      analysisContext2 =
  +          AnalysisContextFactory.oldContextWithCoreAndOptions(options);
  +    }
     }
   
     void setUp() {
  
positive.code: import 'package:analyzer/src/generated/source_io.dart';
  import 'package:analyzer/src/generated/testing/ast_factory.dart';
  import 'package:analyzer/src/generated/testing/element_factory.dart';
  import 'package:unittest/unittest.dart';
  
  import '../reflective_tests.dart';
  
negative.code:     int updateOffset = edit.offset;
      int updateEndOld = updateOffset + edit.length;
      int updateOldNew = updateOffset + edit.replacement.length;
      IncrementalResolver resolver;
      if (AnalysisEngine.instance.useTaskModel) {
        LibrarySpecificUnit lsu = new LibrarySpecificUnit(source, source);
        task.AnalysisCache cache = analysisContext2.analysisCache;
        resolver = new IncrementalResolver(null, cache.get(source),
            cache.get(lsu), unit.element, updateOffset, updateEndOld,
            updateOldNew);
      } else {
        resolver = new IncrementalResolver(
            (analysisContext2 as AnalysisContextImpl)
                .getReadableSourceEntryOrNull(source), null, null, unit.element,
            updateOffset, updateEndOld, updateOldNew);
      }
      bool success = resolver.resolve(newNode);
      expect(success, isTrue);
      List<AnalysisError> newErrors = analysisContext.computeErrors(source);
  