A mobile robot is configured for operation in a commercial or industrial setting, such as an office building or retail store. The mobile robot can have a motorized base and a robot body on the motorized base, the robot body including a rotatable ring that rotates horizontally around the robot body. A mechanical arm that can contract and extend relative to the robot body is coupled to the rotatable ring and performs a plurality of actions. A controller of the mobile robot provides instructions to the rotatable ring and the mechanical arm and can cause the mechanical arm to open a door, take an elevator to move to a different floor, test whether a door is locked properly, and test whether an access control system of the door is working properly.