public void AddDeal_Should_Add_Deal_Item_To_The_List()
{
var dealItem = new DealItem {
ItemNumber = "deal01"
};
_orderManager.AddDeal(dealItem);
var deal = _item.Items.Where(x => x.ItemNumber == dealItem.ItemNumber).SingleOrDefault();
Assert.AreEqual(true, deal.IsDealItem);
}