public void ListAfterInsertingAndRemovingNode_ShouldBeEmpty()
        {
            var list = new DblLinkedList <int>();
            var node = DblLinkedList.CreateNode(1);

            list.InsertTail(node);
            list.Remove(node);
            list.IsEmpty().Should().BeTrue();
        }
        public void AfterRemovingHeadNode_HeadShouldBeChanged()
        {
            var list  = new DblLinkedList <int>();
            var node1 = DblLinkedList.CreateNode(1);
            var node2 = DblLinkedList.CreateNode(2);

            list.InsertHead(node1);
            list.InsertHead(node2);
            list.Remove(node2);
            list.Head.Value.Should().Be(node1.Value);
        }