def METHOD_NAME(self, grib_api, fill_value):
    # Check the use of a mask has been turned on via:
    #   eccodes.codes_set(grib_message, 'bitmapPresent', 1)
    #   eccodes.codes_set_double(grib_message, 'missingValue', fill_value)
    grib_api.codes_set.assert_called_once_with(GRIB_MESSAGE,
                                               'bitmapPresent', 1)
    grib_api.codes_set_double.assert_called_once_with(GRIB_MESSAGE,
                                                      'missingValue',
                                                      fill_value)