def METHOD_NAME(self):
    """
        Test validates return total and used size when has single instance
    """
    self.driver.check_instance_is_master = MagicMock(
        side_effect=self.instance_helper.check_instance_is_master
    )
    self.instance.total_size_in_bytes = 105
    self.instance.used_size_in_bytes = 55
    self.instance.save()
    self.assertEqual(self.driver.masters_total_size_in_bytes, 105)
    expected_total_size_in_gb = 105 * self.GB_FACTOR
    self.assertEqual(self.driver.get_master_instance_total_size_in_gb(), expected_total_size_in_gb)
    self.assertEqual(self.driver.masters_used_size_in_bytes, 55)