Moq: Advanced Mock Setup

Question

I am relatively new to Moq and have this difficult case to taunt and get stuck. I was hoping an experienced Moq user could advise me the following:

Inside my ViewModel model, ctor calls this loading method:

public void LoadCategories()
        {
            Categories = null;
            BookDataService.GetCategories(GetCategoriesCallback);
        }

I would like to mock the Service. But since the service method is invalid and the return always comes through a callback, it becomes too complicated for me.

private void GetCategoriesCallback(ObservableCollection<Category> categories)
        {
            if (categories != null)
            {
                this.Categories = categories;
                if (Categories.Count > 0)
                {
                    SelectedCategory = Categories[0];
                }
                LoadBooksByCategory();
            }
        }

Since it wasn’t as bad as you can see, there is another LoadMethod called LoadBooksByCategory ()

public void LoadBooksByCategory()
        {
            Books = null;
            if (SelectedCategory != null)
                BookDataService.GetBooksByCategory(GetBooksCallback, SelectedCategory.CategoryID, _pageSize);
        }

private void GetBooksCallback(ObservableCollection<Book> books)
        {
            if (books != null)
            {
                if (Books == null)
                {
                    Books = books;
                }
                else
                {
                    foreach (var book in books)
                    {
                        Books.Add(book);
                    }
                }

                if (Books.Count > 0)
                {
                    SelectedBook = Books[0];
                }
            }
        }

So now my setup is Mock:

bool submitted = false;
                Category selectedCategory = new Category{CategoryID = 1};
                ObservableCollection<Book> books;
                var mockDomainClient = new Mock<TestDomainClient>();
                var context = new BookClubContext(mockDomainClient.Object);
                var book = new Book
                {
                 ...
                };

                var entityChangeSet = context.EntityContainer.GetChanges();
                var mockService = new Mock<BookDataService>(context);

                mockService.Setup(s => s.GetCategories(It.IsAny<Action<ObservableCollection<Category>>>()))
                    .Callback<Action<ObservableCollection<Category>>>(action => action(new ObservableCollection<Category>{new Category{CategoryID = 1}}));

                mockService.Setup(s => s.GetBooksByCategory(It.IsAny<Action<ObservableCollection<Book>>>(), selectedCategory.CategoryID, 10))
                    .Callback<Action<ObservableCollection<Book>>>(x => x(new ObservableCollection<Book>()));


                //Act
                var vm = new BookViewModel(mockService.Object);

                vm.AddNewBook(book);
                vm.OnSaveBooks();

                //Assert
                EnqueueConditional(() => vm.Books.Count > 0);
                EnqueueCallback(() => Assert.IsTrue(submitted));

As you can see, I created two settings for each Service call, however, due to their callback and sequential dependency, it is very confusing.

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Answer 1

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public class BookClubContextFixtureHelper
{
    Mock<BookDataService> _mockService;
    ObservableCollection<Category> _categories;

    public BookClubContextFixtureHelper()
    {
        // initialize your context
    }

    public BookDataService Service
    {
       get { return _mockService.Object; }
    }

    public void SetupCategories(param Category[] categories)
    {
         _categories = new ObservableCollection<Category>(categories);

        _mockService
           .Setup( s => s.GetCategories( DefaultInput() )
           .Callback( OnGetCategories )
           .Verifiable();         
    }

    public void VerifyAll()
    {
       _mockService.VerifyAll();
    }

    Action<ObservableCollection<Category>> DefaultInput()
    {
        return It.IsAny<Action<ObservableCollection<Category>>>();
    }

    void OnGetCategories(Action<ObservableCollection<Category>> action)
    {
        action( _categories );
    }
}

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