fix: some errors

test/app/view/app_test.dart

@@ -24,7 +24,7 @@ void main() {
       authenticationRepository = _MockAuthenticationRepository();
       leaderboardRepository = _MockLeaderboardRepository();
       pinballAudio = _MockPinballAudio();
-      when(pinballAudio.load).thenAnswer((_) => Future.value());
+      when(pinballAudio.load).thenAnswer((_) => [Future.value()]);
     });
 
     testWidgets('renders PinballGamePage', (tester) async {

test/helpers/pump_app.dart

@@ -28,7 +28,7 @@ class _MockPinballAudio extends Mock implements PinballAudio {}
 
 PinballAudio _buildDefaultPinballAudio() {
   final audio = _MockPinballAudio();
-  when(audio.load).thenAnswer((_) => Future.value());
+  when(audio.load).thenAnswer((_) => [Future.value()]);
   return audio;
 }