anchor.diff:  import 'package:vm_service/vm_service.dart';
   
   void main() {
  -  MockVmService serviceMock;
  -  StreamController<Map<String, Object>> requestsController;
  -  StreamController<Map<String, Object>> responsesController;
  -  ServiceExtensionRegistry serviceRegistry;
  +  late MockVmService serviceMock;
  +  late StreamController<Map<String, Object>> requestsController;
  +  late StreamController<Map<String, Object?>> responsesController;
  +  late ServiceExtensionRegistry serviceRegistry;
   
     setUp(() {
       serviceMock = MockVmService();
       requestsController = StreamController<Map<String, Object>>();
  -    responsesController = StreamController<Map<String, Object>>();
  +    responsesController = StreamController<Map<String, Object?>>();
       serviceRegistry = ServiceExtensionRegistry();
       VmServerConnection(requestsController.stream, responsesController.sink,
           serviceRegistry, serviceMock);
  
positive.code:         isSystemIsolate: false,
        );
        var request = rpcRequest("setVMTimelineFlags", params: {
          'isolateId': isolate.id,
          // Note: the dynamic list below is intentional in order to exercise the
          // code under test.
          'recordedStreams': <dynamic>['GC', 'Dart', 'Embedder'],
        });
        var response = Success();
        when(serviceMock.getIsolate(isolate.id))
            .thenAnswer((Invocation invocation) {
          expect(invocation.namedArguments,
              equals({Symbol('isolateId'): null, Symbol('args'): null}));
  
negative.code:       expect(responsesController.stream, emits(rpcResponse(version)));
        requestsController.add(request);
      });
      test('works for methods with parameters', () {
        var isolate = Isolate(
          name: 'isolate',
  