public void Add_After_Count_0_Does_Not_Add()
        {
            var linkedList    = new DoubleLinkedList <int>();
            var newNode       = new DoubleLinkedListNode <int>(1);
            var nodeNotInList = new DoubleLinkedListNode <int>(2);

            linkedList.AddAfter(nodeNotInList, newNode);

            linkedList.Count.Should().Be(0);
        }
        public void Can_Add_After_Element()
        {
            var linkedList = new DoubleLinkedList <int>();
            var node1      = new DoubleLinkedListNode <int>(1);
            var node2      = new DoubleLinkedListNode <int>(2);
            var newNode    = new DoubleLinkedListNode <int>(3);

            linkedList.AddFirst(node1);
            linkedList.AddLast(node2);
            linkedList.AddAfter(node1, newNode);

            linkedList.Count.Should().Be(3);
            linkedList.First.Should().Be(node1);
            linkedList.Last.Should().Be(node2);

            linkedList.First.Value.Should().Be(1);
            linkedList.First.Next.Value.Should().Be(3);
            linkedList.Last.Value.Should().Be(2);
            linkedList.Last.Previous.Value.Should().Be(3);
        }