anchor.diff:        StreamController<Response>.broadcast();
     StreamController<Notification> notificationController =
         StreamController<Notification>(sync: true);
  -  Completer<Response> errorCompleter;
  +  Completer<Response>? errorCompleter;
   
     List<Response> responsesReceived = [];
     List<Notification> notificationsReceived = [];
   
     bool _closed = false;
   
  -  String name;
  +  String? name;
   
     MockServerChannel();
   
  
positive.code: // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  // @dart = 2.9
  
  import 'dart:async';
  
  import 'package:analysis_server/protocol/protocol.dart';
  import 'package:analysis_server/src/analysis_server.dart';
  import 'package:analysis_server/src/channel/channel.dart';
  import 'package:analysis_server/src/plugin/notification_manager.dart';
  import 'package:analysis_server/src/plugin/plugin_manager.dart';
  
negative.code: /// A plugin manager that simulates broadcasting requests to plugins by
  /// hard-coding the responses.
  class TestPluginManager implements PluginManager {
    plugin.AnalysisSetPriorityFilesParams? analysisSetPriorityFilesParams;
    plugin.AnalysisSetSubscriptionsParams? analysisSetSubscriptionsParams;
    plugin.AnalysisUpdateContentParams? analysisUpdateContentParams;
    plugin.RequestParams? broadcastedRequest;
    Map<PluginInfo, Future<plugin.Response>>? broadcastResults;
  
    @override
    List<PluginInfo> plugins = [];
  