def METHOD_NAME(self, po, partner, total):
    notification = po.notification_ids.filtered(lambda x: x.partner_id == partner)
    self.assertEqual(len(notification.payment_line_ids), total)
    self.assertIn(partner, notification.mapped("message_follower_ids.partner_id"))
    self.assertIn(self.mt_comment, notification.mapped("message_ids.subtype_id"))