def test_list_files(self, mock_build):
# mock
drive_service = DriveService(self.credentials)
with patch.object(drive_service.service.files(), 'list', return_value=MagicMock()) as mock_list_files:
# act
drive_service.list_files()
# assert
mock_list_files.assert_called_with(fields='nextPageToken, files(id, name)', pageSize=10)
