anchor.diff:          'ext.flutter.brightnessOverride',
           isolateId: isolate.id,
         );
  -      expect(response.json['value'], 'Brightness.light');
  +      expect(response.json?['value'], 'Brightness.light');
   
         final Response updateResponse = await vmService.callServiceExtension(
           'ext.flutter.brightnessOverride',
  
positive.code: 
        flutter = FlutterRunTestDriver(tempDir);
        await flutter.run(withDebugger: true);
        final int port = flutter.vmServicePort;
        vmService = await vmServiceConnectUri('ws://localhost:$port/ws');
      });
  
      tearDown(() async {
        await flutter?.stop();
        tryToDelete(tempDir);
      });
  
  
negative.code: // Copyright 2014 The Flutter Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  import 'package:file/file.dart';
  import 'package:flutter_tools/src/base/file_system.dart';
  