Can an unserviceable component be fitted on a serviceable aircraft for a maintenance check?
EASA Regulations do not specifically preclude you from doing what you are planning to. They leave an awful lot of room for interpretation. How you do your maintenance is up to you, as long as you meet the core requirements and that your processes can be audited.
Additional rules for this type of activity would normally covered by a local procedure (such as Robbery). If you do not have a covering procedure internally then you should absolutely be checking with your Quality Assurance department to validate your actions before undertaking the procedure.