A dead-simple example of how to test a riverpod provider with Mockito. What we have here is a simple class of `cat` that makes a sound. This class has been used via a change notifier provider with the app. On the app, we have an elevated button that on tapping calls the `sound` method.

‎class Cat extends ChangeNotifier {
String sound() => "Meow";
}

After the class is added we need to generate the mocks for the calls. Its simple to do so by using annotation and then calling the build runner from the terminal `flutter pub run build_runner build`

‎@GenerateMocks([Cat])

We now have the provider setup as bellow

final catProvider = ChangeNotifierProvider<Cat>((ref) {‎
return Cat();
}

We now have the setup complete and let write the test

void main() {‎
var mockCat = MockCat();
when(mockCat.sound()).thenReturn('Meow');

testWidgets('Cat mocks correctly', (WidgetTester tester) async {
await tester.pumpWidget(ProviderScope(
overrides: [
catProvider.overrideWithValue(mockCat),
],
child: MaterialApp(
home: Consumer(builder: (context, ref, child) {
final _cat = ref.watch(catProvider);
return ElevatedButton(
key: Key("make_sound"),
onPressed: () async {
try {
_cat.sound();
}catch(err){}
},
child: const Text('Make Sound'),
);
}),
),
));

await tester.tap(find.byKey(Key("make_sound")));
verify(mockCat.sound()).called(1);

});
}

Run the test make sure that the method sound() in the provider is called correctly up on clicking the button.