def test_deleting_only_node_should_leave_the_tree_empty():
object_under_test = RedBlackTree()
object_under_test.insert(22)
object_under_test.delete(22)
assert not object_under_test.traverse_preorder()
def test_given_elements_then_traverse_preorder_should_return_elements_in_preorder_with_parents_first(
input_elements, expected_output):
object_under_test = RedBlackTree()
for ele in input_elements:
object_under_test.insert(value=ele)
assert expected_output == object_under_test.traverse_preorder()