public void List_ThrowsErrorIfAddingAtAnInvalidIndex()
        {
            var circular = new CircularLinkedList <int>();

            circular.AddLast(30);
            circular.AddLast(40);

            Assert.Throws <IndexOutOfRangeException>(() => circular.AddAt(-1, 100));
            Assert.Throws <IndexOutOfRangeException>(() => circular.AddAt(3, 100));
        }
        public void List_CanInsertAtACorrectIndex()
        {
            var circular = new CircularLinkedList <int>();

            circular.AddLast(30);
            circular.AddLast(40);
            circular.AddLast(50);
            circular.AddAt(1, 100);

            Assert.Equal(4, circular.Size);
            Assert.Equal(100, circular.GetAt(1).Value);
        }