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);
}