Public Class LListNode(Of T) 
   Inherits LListNode

public class LListNode<T> : LListNode 

LListNode<string> empty = new LListNode<string>();
LListNode<string> valueA = new LListNode<string>("A");
LListNode<string> valueB = new LListNode<string>("B");
LListNode<string>.LList list = new LListNode<string>.LList();

list.AddFirst(empty);
Assert.AreEqual(1, list.Count);
Assert.AreEqual(empty, list.First);
Assert.AreEqual(empty, list.Last);
Assert.IsNull(empty.Next);
Assert.IsNull(empty.Previous);

list.AddLast(valueB);
Assert.AreEqual(2, list.Count);
Assert.AreEqual(empty, list.First);
Assert.AreEqual(valueB, list.Last);

Assert.AreEqual(valueB, empty.Next);
Assert.IsNull(empty.Previous);

Assert.AreEqual(empty, valueB.Previous);
Assert.IsNull(valueB.Next);

list.AddFirst(valueA);
Assert.AreEqual(3, list.Count);
Assert.AreEqual(valueA, list.First);
Assert.AreEqual(valueB, list.Last);

Assert.AreEqual(valueB, empty.Next);
Assert.AreEqual(valueA, empty.Previous);

Assert.AreEqual(empty, valueA.Next);
Assert.IsNull(valueA.Previous);

Assert.AreEqual(empty, valueB.Previous);
Assert.IsNull(valueB.Next);

list.Remove(empty);
Assert.AreEqual(2, list.Count);
Assert.AreEqual(valueA, list.First);
Assert.AreEqual(valueB, list.Last);

Assert.AreEqual(valueB, valueA.Next);
Assert.IsNull(valueA.Previous);

Assert.AreEqual(valueA, valueB.Previous);
Assert.IsNull(valueB.Next);

Dim empty As New LListNode(Of String)()
Dim valueA As New LListNode(Of String)("A")
Dim valueB As New LListNode(Of String)("B")
Dim list As New LListNode(Of String).LList()

list.AddFirst(empty)
Assert.AreEqual(1, list.Count)
Assert.AreEqual(empty, list.First)
Assert.AreEqual(empty, list.Last)
Assert.IsNull(empty.[Next])
Assert.IsNull(empty.Previous)

list.AddLast(valueB)
Assert.AreEqual(2, list.Count)
Assert.AreEqual(empty, list.First)
Assert.AreEqual(valueB, list.Last)

Assert.AreEqual(valueB, empty.[Next])
Assert.IsNull(empty.Previous)

Assert.AreEqual(empty, valueB.Previous)
Assert.IsNull(valueB.[Next])

list.AddFirst(valueA)
Assert.AreEqual(3, list.Count)
Assert.AreEqual(valueA, list.First)
Assert.AreEqual(valueB, list.Last)

Assert.AreEqual(valueB, empty.[Next])
Assert.AreEqual(valueA, empty.Previous)

Assert.AreEqual(empty, valueA.[Next])
Assert.IsNull(valueA.Previous)

Assert.AreEqual(empty, valueB.Previous)
Assert.IsNull(valueB.[Next])

list.Remove(empty)
Assert.AreEqual(2, list.Count)
Assert.AreEqual(valueA, list.First)
Assert.AreEqual(valueB, list.Last)

Assert.AreEqual(valueB, valueA.[Next])
Assert.IsNull(valueA.Previous)

Assert.AreEqual(valueA, valueB.Previous)
Assert.IsNull(valueB.[Next])