에러 메시지
/C:/dev/src/flutter/.pub-cache/hosted/pub.dartlang.org/video_player_platform_interface-2.2.0/lib/messages.dart:432:15: Error: The method 'setMockMessageHandler' isn't defined for the class 'BasicMessageChannel'.
- 'BasicMessageChannel' is from 'package:flutter/src/services/platform_channel.dart' ('/C:/dev/src/flutter/packages/flutter/lib/src/services/platform_channel.dart').
Try correcting the name to the name of an existing method, or defining a method named 'setMockMessageHandler'.
channel.setMockMessageHandler((dynamic message) async {
^^^^^^^^^^^^^^^^^^^^^
해결
flutter pub upgrade