public void UpdateQuantityTest()
{
int totalPrice = 0;
totalPrice += _itemInfo.GetItemPrice("item0");
_itemOrder.AddToOrder("item0");
Assert.AreEqual(totalPrice, _itemOrder.GetTotalPrice());
Assert.AreEqual(10, _itemOrder.UpdateQuantity(0, 10));
Assert.AreEqual(totalPrice * 10, _itemOrder.GetTotalPrice());
Assert.AreEqual(10, _itemOrder.UpdateQuantity(0, 20));
Assert.AreEqual(totalPrice * 10, _itemOrder.GetTotalPrice());
Assert.AreEqual(1, _itemOrder.UpdateQuantity(0, 1));
Assert.AreEqual(totalPrice, _itemOrder.GetTotalPrice());
Assert.AreEqual(0, _itemOrder.UpdateQuantity(-1, 10));
Assert.AreEqual(totalPrice, _itemOrder.GetTotalPrice());
Assert.AreEqual(0, _itemOrder.UpdateQuantity(1, 10));
Assert.AreEqual(totalPrice, _itemOrder.GetTotalPrice());
}