public void PopBack()
        {
            DLinkedList<int> list = new DLinkedList<int>();
            int expectedResult = 2, result;

            list.PushFront(1);
            list.PushFront(2);
            list.PushFront(3);
            list.PopBack();

            result = list.OnBack();

            Assert.AreEqual(expectedResult, result);
        }
 public void PopBack_ListIsEmptyThrowsException()
 {
     DLinkedList<int> emptyList = new DLinkedList<int>();
     emptyList.PopBack();
 }