public void LoadCategories_calles_categoryRepository_GetAll()
        {
            var unitOfWork         = Substitute.For <IUnitOfWork>();
            var categoryRepository = Substitute.For <ICategoryRepository>();

            unitOfWork.Categories.Returns(categoryRepository);
            var eventAggregator = Substitute.For <IEventAggregator>();

            var vm = new CategoriesViewModel(unitOfWork, eventAggregator);

            vm.LoadCategories();

            categoryRepository.Received().GetAll(asNoTracking: true);
        }