anchor.diff:    }
   
     void test_applySingleChange() {
  -    resourceProvider.getFile('/test.dart').writeAsStringSync('void main() {}');
  +    getFile('/test.dart').writeAsStringSync('void main() {}');
       dartfixListener.addSourceChange(
           "test change",
           Location('/test.dart', 10, 0, 1, 10),
  
positive.code: @reflectiveTest
  class PreviewSiteTest {
    PreviewSite site;
    ResourceProvider resourceProvider;
    DartFixListener dartfixListener;
    MigrationState state;
  
    void setUp() {
      dartfixListener = DartFixListener(null);
  
negative.code:   }
  
    void test_applyMultipleChanges() {
      getFile('/test.dart').writeAsStringSync('void main() {}');
      dartfixListener.addSourceChange(
          "test change",
          Location('/test.dart', 10, 0, 1, 10),
  