def test_count_children(self):
tree = BinaryTree()
node1 = Node((1, None))
node2 = Node((5, None))
node3 = Node((7, None))
node4 = Node((4, None))
tree.insert(node1)
tree.insert(node2)
tree.insert(node3)
tree.insert(node4)
self.assertEqual(tree._count_children(node2), 2)
self.assertEqual(tree._count_children(node1), 1)
