public void AddAtWrongIndex()
{
string expected = "1/2/4/5/";
DoublyLinkedList testList = new DoublyLinkedList();
testList.AddLast("1");
testList.AddLast("2");
testList.AddLast("4");
testList.AddLast("5");
testList.AddAtIndex("3", 7);
string actual = testList.Show();
Assert.AreEqual(expected, actual);
}