public void Clear()
 {
     DoublyLinkedList<int> list = new DoublyLinkedList<int>();
     list.Add(3);
     list.Add(5);
     list.Add(7);
     list.Clear();
     list.ShouldBeEmpty();
 }
 public void RemoveForASingleItemList()
 {
     DoublyLinkedList<int> list = new DoublyLinkedList<int>();
     list.AddAtTail(7);
     list.Remove(7);
     list.ShouldBeEmpty();
 }
 public void EmptyList()
 {
     DoublyLinkedList<int> list = new DoublyLinkedList<int>();
     list.ShouldBeEmpty();
 }