//this method test RemoveTail() function
        public void PushBack23_3returned()
        {
            int expected = 3;
            int list_buffer;

            simple_ds.Structures.DoubleLinkedList <int> list = new simple_ds.Structures.DoubleLinkedList <int>();

            for (var number = 2; number <= 3; ++number)
            {
                list.PushBack(number);
            }

            list_buffer = list.RemoveTail();

            Assert.AreEqual(expected, list_buffer);
        }