Unable to mock Notifier state used in widget test

[mstagitis]

Hi all - I understand that mocking Notifier's isn't generally recommended, but I do believe it's the correct thing to do given my situation. I am writing a widget test for a widget that watches an AutoDisposeAsyncNotifier that holds some state and has methods for interacting with the state.

Here is a simple example below:

class MyNotifier extends AutoDisposeAsyncNotifier<SomeState> {
  @override
  Future<SomeState> build() async {
    ...
  }

  Future<void> someAction() async {
    ...
  }
}

final myProvider = AutoDisposeAsyncNotifierProvider<MyNotifier, SomeState>(MyNotifier.new);

class MyScreen extends ConsumerStatefulWidget {
  ...
}

class _MyScreenState extends ConsumerState<MyScreen> {
  @override
  Widget build(BuildContext context) {
    return Column(children: [
      Text(ref.watch(myProvider).value),
      OutlinedButton(
        onPressed: () {
          ref.read(myProvider.notifier).someAction();
        },
        child: Text('Press me')
      )
    ]);
  }
}

I want to mock out both the notifier's someAction() call and its state. If I only override the notifier, then the overriding implementation needs to implement someAction(), which brings notifier-specific code into a widget test. Ideally this widget test will cover only the widget-specific code, with all dependencies mocked out.

I've tried the following:

class MockMyNotifier extends AutoDisposeAsyncNotifier<SomeState> with Mock implements MyNotifier {}

void main() {
  testWidgets('A test', (WidgetTester tester) async {
    MockMyNotifier mockMyNotifier = MockMyNotifier();
    when(() => mockMyNotifier.someAction()).thenAnswer((_) async => Future.value());   # <-- This works
    when(() => mockMyNotifier.state)
        .thenAnswer((_) => AsyncValue.data(someState));    # <-- This throws the error below
    ...
  });
}

The thrown error:

══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following LateError was thrown running a test:
LateInitializationError: Field '_element@169502701' has not been initialized.

When the exception was thrown, this was the stack:
#0      BuildlessAutoDisposeAsyncNotifier._element (package:riverpod/src/async_notifier/auto_dispose.dart)
#1      AsyncNotifierBase.state (package:riverpod/src/async_notifier.dart:48:5)
...

Has anyone had luck with mocking out a notifier's state? Thanks ahead of time!
Matt

[MickaelBenasse]

Hi,

I have currently the same problem, did you ever find a solution about this ? @mstagitis