def test_is_empty(self):
     s = test_items_seq()
     tree = AnderssonTree()
     self.assertTrue(tree.is_empty())
     tree.update(s)
     self.assertFalse(tree.is_empty())
     tree.clear()
     self.assertTrue(tree.is_empty())
 def test_clear(self):
     s = test_items_seq()
     tree = AnderssonTree(s)
     self.check_aatree_properties(tree)
     tree.clear()
     self.assertEqual(len(tree), 0)