Mock Flutter Bloc initial state using Mockito

// Test Dependencies
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:mockito/mockito.dart';

// TodoList Dependencies
import 'package:todolist/widgets/todo_list.dart';
import 'package:todolist/blocs/todo_list/bloc.dart';
import 'package:todolist/blocs/todo_list/state.dart';

class MockTodoListBloc extends Mock implements TodoListBloc {}

void main() {
  // Testing the TodoList widget
  group('TodoList', () {

    // Test how it reacts when the Bloc state is TodoLoadingState
    group('TodoLoadingState', () {
      testWidgets('should render a loading icon when handling the TodoLoadingState', (WidgetTester tester) async {
        // Setup the mock bloc
        TodoListBloc todoListBloc = MockTodoListBloc();

        // Mock the injected TodoListBloc state.
        // See _BlocBuilderBaseState for how it uses currentState to setup the state
        when(todoListBloc.currentState).thenReturn(TodoLoadingState());

        // Wrap our widget test with a BlocProvider since our widget depends
        // on a BlocBuilder. Our mock TodoListBloc will be passed
        await tester.pumpWidget(
          MaterialApp(
            home: BlocProvider<TodoListBloc>(
              builder: (context) => todoListBloc,
              child: TodoList(),
            ),
          )
        );

        expect(find.byType(CircularProgressIndicator), findsOneWidget);
      });
    });

    // Test how it reacts when the Bloc state is TodoLoadingState
    group('TodoLoadedState', () {
      testWidgets('should render a ListView of ListTile todos when TodoLoadedState', (WidgetTester tester) async {
        // Mock our todo list items
        final List<String> todos = [ "Take out the trash", "Feed the cat" ];

        // Setup the mock bloc
        TodoListBloc todoListBloc = MockTodoListBloc();

        // Mock the injected TodoListBloc state and pass our mock todo list items.
        // See _BlocBuilderBaseState for how it uses currentState to setup the state
        when(todoListBloc.currentState).thenReturn(TodoLoadedState(
          todos: todos
        ));

        // Wrap our widget test with a BlocProvider since our widget depends
        // on a BlocBuilder. Our mock TodoListBloc will be passed
        await tester.pumpWidget(
          MaterialApp(
            home: BlocProvider<TodoListBloc>(
              builder: (context) => todoListBloc,
              child: TodoList(),
            ),
          )
        );

        expect(find.byType(ListView), findsOneWidget);
        expect(find.byType(ListTile), findsNWidgets(todos.length));
      });
    });
  });
}