anchor.diff:      await resolveTestUnit('''
   import 'a/bb/my_lib.dart';
   ''');
  -    AnalysisError error = _findErrorToFix();
  +    AnalysisError error = await _findErrorToFix();
       fix = await _assertHasFix(DartFixKind.CREATE_FILE, error);
       change = fix.change;
       // validate change
  
positive.code:   }
  
    assertHasFix(FixKind kind, String expected) async {
      AnalysisError error = _findErrorToFix();
      fix = await _assertHasFix(kind, error);
      change = fix.change;
      // apply to "file"
  
negative.code:   d.foo(e);
  }
  ''');
      AnalysisError error = await _findErrorToFix();
      fix = await _assertHasFix(DartFixKind.CREATE_METHOD, error);
      change = fix.change;
      // apply to "test2.dart"
  