How to test a ValueNotifier value from a stream? - flutter

Question

Problem
I'm developing a simple Todo app and trying to create test for my files before I develop the UI.
I created a repository which exposes a Stream<List<Todo>>> and I'm listening to it in the TodosOverviewStore. I tried to test if the Store.value would update when the repository stream emitted a new value, but I can't get it right.
Code
todo_repository_impl.dart
import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';
import '../domain/entities/todo.dart';
import '../domain/repositories/todo_repository.dart';
class TodoRepositoryImpl implements TodoRepository {
final SharedPreferences _prefs;
#visibleForTesting
static const String todoKey = '__todo_key__';
TodoRepositoryImpl({required SharedPreferences prefs}) : _prefs = prefs {
_init();
}
final _controller = StreamController<List<Todo>>();
void _init() {
final result = _prefs.getString(todoKey);
if (result == null || result.isEmpty) return _controller.add([]);
final todos = jsonDecode(result).map((e) => Todo.fromMap(e)).toList();
return _controller.add(todos);
}
#override
Stream<List<Todo>> getTodos() => _controller.stream;
}
todos_overview_store.dart
import 'dart:async';
import 'package:flutter/material.dart';
import '../../domain/entities/todo.dart';
import '../../domain/repositories/todo_repository.dart';
class TodosOverviewStore extends ValueNotifier<List<Todo>> {
final TodoRepository _repository;
late final StreamSubscription<List<Todo>> _subscription;
TodosOverviewStore({required TodoRepository todoRepository})
: _repository = todoRepository,
super([]);
void subscriptionRequested() {
_subscription = _repository.getTodos().listen((event) => value = event);
}
#override
Future<void> dispose() async {
await _subscription.cancel();
super.dispose();
}
}
todos_overview_store_test.dart
import 'dart:async';
import 'package:flutter_test/flutter_test.dart';
import 'package:hiveleak/domain/entities/todo.dart';
import 'package:hiveleak/domain/repositories/todo_repository.dart';
import 'package:hiveleak/presentation/stores/todos_overview_store.dart';
import 'package:mocktail/mocktail.dart';
class TodoRepositoryMock extends Mock implements TodoRepository {}
main() {
final todoRepository = TodoRepositoryMock();
late TodosOverviewStore todosOverviewStore;
final todo = Todo(title: 'lorem ipsum', done: false);
group('subscriptionRequested', () {
when(() => todoRepository.getTodos())
.thenAnswer((_) => Stream.value([todo]));
setUp(() {
todosOverviewStore = TodosOverviewStore(todoRepository: todoRepository);
});
test('It should call todoRepository.getTodos', () {
todosOverviewStore.subscriptionRequested();
verify(() => todoRepository.getTodos()).called(1);
});
test('It should update its value when stream emits', () {
todosOverviewStore.subscriptionRequested();
expect(todosOverviewStore.value, equals([todo]));
});
});
}
Error
But when I run this test, I get the following result:
package:test_api expect
package:flutter_test/src/widget_tester.dart 460:16 expect
test\presentation\stores\todos_overview_store_test.dart 34:7 main.<fn>.<fn>
Expected: [Instance of 'Todo']
Actual: []
Which: at location [0] is [] which shorter than expected
What should I do to make this work ? Thanks in advance.