public void SizeTest()
        {
            BinTree<int> tree = new BinTree<int>(new BinNode<int>(10));
            tree.InsertAsLC(tree.Root(), 15);
            Assert.IsTrue(tree.Size() == 2, "2");

            tree = new BinTree<int>(null);
            Assert.IsTrue(tree.Size() == 0);
        }