public void ItemService_NullStrings_NullException()
{
//arrange
var dataConverter = new Mock <IDataConverter>();
var dataManager = new Mock <IItemManager>();
var itemCategorization = new Mock <IItemCategorization>();
ItemService itemService = new ItemService(dataConverter.Object, dataManager.Object, itemCategorization.Object);
//act
//assert
Assert.Throws <NullReferenceException>(() => itemService.AddCategory(null, null));
}