Literature summary: commissioning is a quality-assurance process that verifies systems are installed and operate according to defined requirements. It is strongest when acceptance criteria, responsibilities and test methods are written before the result is known.
Functional testing checks cause and response across relevant modes: occupied and unoccupied schedules, staging, alarms, safeties, ventilation, cooling, recovery and failure response. A screen command is not proof that a damper, fan, valve or zone physically responded.
Issues remain open until correction and retest. Replacing a component can restore operation without restoring sequence, airflow, moisture control or the occupied result, so evidence should connect the repair to the original requirement.
Measurement and verification addresses performance after implementation. Baselines, boundary conditions and operating changes matter; commissioning proves intended function, while energy-savings claims require a separate suitable M&V plan.