@mock.patch.object(cli, '_use_separate_migration_branches',
                       return_value=True)
    @mock.patch.object(fileutils, 'delete_if_exists')
    def test_update_head_files_success(self, *mocks):
        heads = ['a', 'b']
        mock_open_con = self.useFixture(
                    tools.OpenFixture(cli._get_contract_head_file_path(
                        self.configs[0]))).mock_open
        mock_open_ex = self.useFixture(
            tools.OpenFixture(cli._get_expand_head_file_path(
                self.configs[0]))).mock_open
        with mock.patch('alembic.script.ScriptDirectory.from_config') as fc:
            fc.return_value.get_heads.return_value = heads
            revs = {heads[0]: FakeRevision(labels=cli.CONTRACT_BRANCH),
                    heads[1]: FakeRevision(labels=cli.EXPAND_BRANCH)}
            fc.return_value.get_revision.side_effect = revs.__getitem__
            cli.update_head_files(self.configs[0])
            mock_open_con.return_value.write.assert_called_with(
                heads[0] + '\n')
            mock_open_ex.return_value.write.assert_called_with(heads[1] + '\n')

            old_head_file = cli._get_head_file_path(
                self.configs[0])
            old_heads_file = cli._get_heads_file_path(
                self.configs[0])
            delete_if_exists = mocks[0]
            self.assertIn(mock.call(old_head_file),
                          delete_if_exists.call_args_list)
            self.assertIn(mock.call(old_heads_file),
                          delete_if_exists.call_args_list)
dataset/ETHPy150Open openstack/neutron/neutron/tests/unit/db/test_migration.py/TestCli.test_update_head_files_success/original