anchor.diff:    SystemChannels.navigation
         .setMockMethodCallHandler((MethodCall methodCall) async {});
   
  -  ServicesBinding.instance.defaultBinaryMessenger
  -      .setMockMessageHandler('flutter/assets', (ByteData message) async {
  +  ServicesBinding.instance!.defaultBinaryMessenger
  +      .setMockMessageHandler('flutter/assets', (ByteData? message) async {
       assert(message != null);
  -    String key = utf8.decode(message.buffer.asUint8List());
  -    File asset = File(path.join(assetFolderPath, key));
  +    String key = utf8.decode(message!.buffer.asUint8List());
  +    File asset = File(path.join(assetFolderPath!, key));
   
       if (!asset.existsSync()) {
         // For tests in package, it will load assets with its own package prefix.
  
positive.code:   if (!Platform.environment.containsKey('UNIT_TEST_ASSETS')) {
      return;
    }
    final String assetFolderPath = Platform.environment['UNIT_TEST_ASSETS'];
    assert(Platform.environment['APP_NAME'] != null);
    final String prefix = 'packages/${Platform.environment['APP_NAME']}/';
  
  
negative.code: ///
  /// Tests that `listener` has actually been invoked.
  Future<void> addListenerScope({
    required dynamic listenable,
    required Function listener,
    required Function callback,
  }) async {
    bool listenerCalled = false;
    final listenerWrapped = () {
  