It is usually dependent on the terms of your lease if you or your landlord are responsible for paying for electrical testing to be carried out. If you are going to rent a property then this is always something that should be agreed and included in the tenancy document beforehand. If you are on a full repairing lease then the cost will fall to you. Always remember that you are responsible to make sure that you and your staff comply with Health & Safety legislation and The Electricity at Work Regulations 1989.