def test_add_subpart_children(self):
        """Can correctly add layer data to subparts"""
        message = {'99-1': [1, 2], '99-1-a': [3, 4]}
        l1, l2, l3, l4 = self.put_with_mock_data(
            message, '99', '99-Subpart-A', '99-1', '99-1-a',