Add explicit null returns in flutter/test (#94834)

packages/flutter/test/cupertino/picker_test.dart

@@ -226,6 +226,7 @@ void main() {
 
         tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
           systemCalls.add(methodCall);
+          return null;
         });
 
         await tester.pumpWidget(
@@ -279,6 +280,7 @@ void main() {
 
         tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
           systemCalls.add(methodCall);
+          return null;
         });
 
         await tester.pumpWidget(

packages/flutter/test/cupertino/refresh_test.dart

@@ -177,6 +177,7 @@ void main() {
 
       tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
         platformCallLog.add(methodCall);
+        return null;
       });
 
       await tester.pumpWidget(

packages/flutter/test/cupertino/scrollbar_test.dart

@@ -137,6 +137,7 @@ void main() {
       if (methodCall.method == 'HapticFeedback.vibrate') {
         hapticFeedbackCalls += 1;
       }
+      return null;
     });
 
     // Long press on the scrollbar thumb and expect a vibration after it resizes.
@@ -777,6 +778,7 @@ void main() {
       if (methodCall.method == 'HapticFeedback.vibrate') {
         hapticFeedbackCalls += 1;
       }
+      return null;
     });
 
     // Long press on the scrollbar thumb and expect a vibration after it resizes.

packages/flutter/test/cupertino/switch_test.dart

@@ -53,6 +53,7 @@ void main() {
 
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(
@@ -93,6 +94,7 @@ void main() {
 
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(
@@ -160,6 +162,7 @@ void main() {
 
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(
@@ -198,6 +201,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(

packages/flutter/test/cupertino/text_field_test.dart

@@ -3248,6 +3248,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(
@@ -3271,6 +3272,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(
@@ -4359,6 +4361,7 @@ void main() {
           actions: <Type, Action<Intent>>{
             ScrollIntent: CallbackAction<ScrollIntent>(onInvoke: (Intent intent) {
               scrollInvoked = true;
+              return null;
             }),
           },
           child: ListView(

packages/flutter/test/material/text_field_test.dart

@@ -9841,6 +9841,7 @@ void main() {
           actions: <Type, Action<Intent>>{
             ScrollIntent: CallbackAction<ScrollIntent>(onInvoke: (Intent intent) {
               scrollInvoked = true;
+              return null;
             }),
           },
           child: Material(

packages/flutter/test/rendering/first_frame_test.dart

@@ -18,6 +18,7 @@ void main() {
     const MethodChannel firstFrameChannel = MethodChannel('flutter/service_worker');
     binding.defaultBinaryMessenger.setMockMethodCallHandler(firstFrameChannel, (MethodCall methodCall) async {
       completer.complete();
+      return null;
     });
 
     binding.handleBeginFrame(Duration.zero);

packages/flutter/test/rendering/mouse_tracker_cursor_test.dart

@@ -57,8 +57,10 @@ void main() {
   setUp(() {
     _binding.postFrameCallbacks.clear();
     _binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.mouseCursor, (MethodCall call) async {
-      if (_methodCallHandler != null)
+      if (_methodCallHandler != null) {
         return _methodCallHandler!(call);
+      }
+      return null;
     });
   });
 

packages/flutter/test/services/default_binary_messenger_test.dart

@@ -41,6 +41,7 @@ void main() {
       (ByteData? message) async {
         expect(message, bar);
         countInbound += 1;
+        return null;
       },
     );
     expect(countInbound, equals(0));

packages/flutter/test/services/deferred_component_test.dart

@@ -13,6 +13,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.deferredComponent, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await DeferredComponent.installDeferredComponent(componentName: 'testComponentName');
@@ -29,6 +30,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.deferredComponent, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await DeferredComponent.uninstallDeferredComponent(componentName: 'testComponentName');

packages/flutter/test/services/haptic_feedback_test.dart

@@ -13,6 +13,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await HapticFeedback.vibrate();
@@ -27,6 +28,7 @@ void main() {
 
       TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
         log.add(methodCall);
+        return null;
       });
 
       await hapticFunction();

packages/flutter/test/services/restoration_test.dart

@@ -66,6 +66,7 @@ void main() {
       final List<MethodCall> callsToEngine = <MethodCall>[];
       tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.restoration, (MethodCall call) async {
         callsToEngine.add(call);
+        return null;
       });
       final RestorationManager manager = RestorationManager();
 

packages/flutter/test/services/system_chrome_test.dart

@@ -14,6 +14,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     // The first call is a cache miss and will queue a microtask
@@ -71,6 +72,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setPreferredOrientations(<DeviceOrientation>[
@@ -89,6 +91,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setApplicationSwitcherDescription(
@@ -107,6 +110,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMessageHandler('flutter/platform', (ByteData? message) async {
       log.add(message);
+      return null;
     });
 
     await SystemChrome.setApplicationSwitcherDescription(
@@ -121,6 +125,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setEnabledSystemUIOverlays(<SystemUiOverlay>[SystemUiOverlay.top]);
@@ -137,6 +142,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setEnabledSystemUIMode(SystemUiMode.leanBack);
@@ -165,6 +171,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setEnabledSystemUIMode(SystemUiMode.manual, overlays: <SystemUiOverlay>[SystemUiOverlay.top]);
@@ -181,6 +188,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemChrome.setSystemUIChangeCallback(null);

packages/flutter/test/services/system_navigator_test.dart

@@ -20,6 +20,7 @@ void main() {
   test('System navigator control test - platform messages', () async {
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await verify(() => SystemNavigator.pop(), <Object>[
@@ -32,6 +33,7 @@ void main() {
   test('System navigator control test - navigation messages', () async {
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await verify(() => SystemNavigator.selectSingleEntryHistory(), <Object>[

packages/flutter/test/services/system_sound_test.dart

@@ -14,6 +14,7 @@ void main() {
 
     TestDefaultBinaryMessengerBinding.instance!.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await SystemSound.play(SystemSoundType.click);

packages/flutter/test/widgets/draggable_test.dart

@@ -3116,6 +3116,7 @@ Future<void> _testLongPressDraggableHapticFeedback({ required WidgetTester teste
     if (methodCall.method == 'HapticFeedback.vibrate') {
       hapticFeedbackCalls++;
     }
+    return null;
   });
 
   await tester.pumpWidget(MaterialApp(

packages/flutter/test/widgets/editable_text_test.dart

@@ -2207,6 +2207,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.showKeyboard(find.byType(EditableText));
@@ -3502,6 +3503,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final TextEditingController controller = TextEditingController();
@@ -3531,6 +3533,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final TextEditingController controller = TextEditingController();
@@ -3566,6 +3569,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final TextEditingController controller1 = TextEditingController();
@@ -3651,6 +3655,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     const Offset offset = Offset(10.0, 20.0);
@@ -3693,6 +3698,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final TextEditingController controller = TextEditingController();
@@ -3780,6 +3786,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
     setState(() {
       currentTextStyle = textStyle2;
@@ -4007,6 +4014,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final TextEditingController controller = TextEditingController();
@@ -6706,6 +6714,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
     final TextInputFormatter formatter = TextInputFormatter.withFunction((TextEditingValue oldValue, TextEditingValue newValue) {
       if (newValue.text == 'I will be modified by the formatter.') {
@@ -6834,6 +6843,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
     final TextInputFormatter formatter = TextInputFormatter.withFunction((TextEditingValue oldValue, TextEditingValue newValue) {
       return const TextEditingValue(text: 'Flutter is the best!');
@@ -6913,6 +6923,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
     final TextEditingController controller = TextEditingController();
 
@@ -7034,6 +7045,7 @@ void main() {
       final List<MethodCall> log = <MethodCall>[];
       tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.textInput, (MethodCall methodCall) async {
         log.add(methodCall);
+        return null;
       });
       final TextEditingController controller = TextEditingController();
 
@@ -8635,7 +8647,7 @@ void main() {
     );
     bool myIntentWasCalled = false;
     final CallbackAction<ExtendSelectionByCharacterIntent> overrideAction = CallbackAction<ExtendSelectionByCharacterIntent>(
-      onInvoke: (ExtendSelectionByCharacterIntent intent) { myIntentWasCalled = true; },
+      onInvoke: (ExtendSelectionByCharacterIntent intent) { myIntentWasCalled = true; return null; },
     );
     await tester.pumpWidget(MaterialApp(
       home: Align(
@@ -8690,7 +8702,7 @@ void main() {
           child: Actions(
             actions: <Type, Action<Intent>>{
               ExtendSelectionByCharacterIntent: CallbackAction<ExtendSelectionByCharacterIntent>(
-                onInvoke: (ExtendSelectionByCharacterIntent intent) { myIntentWasCalled = true; },
+                onInvoke: (ExtendSelectionByCharacterIntent intent) { myIntentWasCalled = true; return null; },
               ),
             },
             child: EditableText(

packages/flutter/test/widgets/modal_barrier_test.dart

@@ -160,8 +160,10 @@ void main() {
     final List<String> playedSystemSounds = <String>[];
     try {
       tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (MethodCall methodCall) async {
-        if (methodCall.method == 'SystemSound.play')
+        if (methodCall.method == 'SystemSound.play') {
           playedSystemSounds.add(methodCall.arguments as String);
+	}
+        return null;
       });
 
       final Widget subject = Stack(

packages/flutter/test/widgets/mouse_region_test.dart

@@ -1621,6 +1621,7 @@ void main() {
     addTearDown(gesture.removePointer);
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.mouseCursor, (_) async {
       logCursors.add('cursor');
+      return null;
     });
 
     final GlobalKey key = GlobalKey();

packages/flutter/test/widgets/route_notification_messages_test.dart

@@ -57,6 +57,7 @@ void main() {
 
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(MaterialApp(
@@ -115,6 +116,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(Directionality(
@@ -165,6 +167,7 @@ void main() {
 
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(MaterialApp(
@@ -223,6 +226,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     await tester.pumpWidget(MaterialApp(
@@ -266,6 +270,7 @@ void main() {
     final List<MethodCall> log = <MethodCall>[];
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.navigation, (MethodCall methodCall) async {
       log.add(methodCall);
+      return null;
     });
 
     final PlatformRouteInformationProvider provider = PlatformRouteInformationProvider(