anchor.diff:    }
   
     void test_applySingleChange() {
  -    getFile('/test.dart').writeAsStringSync('void main() {}');
  +    final path = convertPath('/test.dart');
  +    final file = getFile(path);
  +    file.writeAsStringSync('void main() {}');
       dartfixListener.addSourceChange(
  -        "test change",
  -        Location('/test.dart', 10, 0, 1, 10),
  -        SourceChange("test change", edits: [
  -          SourceFileEdit('/test.dart', 0,
  -              edits: [SourceEdit(10, 0, 'List args')])
  +        'test change',
  +        Location(path, 10, 0, 1, 10),
  +        SourceChange('test change', edits: [
  +          SourceFileEdit(path, 0, edits: [SourceEdit(10, 0, 'List args')])
           ]));
       site.performApply();
  -    expect(getFile('/test.dart').readAsStringSync(), 'void main(List args) {}');
  +    expect(file.readAsStringSync(), 'void main(List args) {}');
       expect(state.hasBeenApplied, true);
     }
   }
  
positive.code: }
  
  @reflectiveTest
  class PreviewSiteTest {
    PreviewSite site;
    MemoryResourceProvider resourceProvider;
    DartFixListener dartfixListener;
    MigrationState state;
  
    File getFile(String path) =>
        resourceProvider.getFile(resourceProvider.convertPath(path));
  
    void setUp() {
      dartfixListener = DartFixListener(null);
  
negative.code: import 'package:analysis_server/src/edit/nnbd_migration/migration_state.dart';
  import 'package:analysis_server/src/edit/nnbd_migration/path_mapper.dart';
  import 'package:analysis_server/src/edit/preview/preview_site.dart';
  import 'package:analyzer/file_system/memory_file_system.dart';
  import 'package:analyzer_plugin/protocol/protocol_common.dart';
  import 'package:test/test.dart';
  import 'package:test_reflective_loader/test_reflective_loader.dart';
  import 'package:analyzer/src/test_utilities/resource_provider_mixin.dart';
  
  void main() {
    defineReflectiveSuite(() {
  