public void TestGetEnumerator()
{
//Assign
list.AddFirst(1);
list.AddLast(2);
//Act
IEnumerator <Node <int> > i = list.GetEnumerator();
//Assert
i.MoveNext();
Assert.AreEqual(i.Current.Data, 1);
i.MoveNext();
Assert.AreEqual(i.Current.Data, 2);
}