Fire Alarm testing should be carried out in house by a responsible person on a weekly basis. BS 5839-1:2017 suggests that your fire alarm system should be inspected at least every 6 months by a fire alarm and emergency testing engineer.
This maintenance needs to be carried out by an experienced professional. All fire alarm sensors must be calibrated and tested, as must annunciators. Batteries should be checked for corrosion and the connection to the fire service checked.