After radical mastectomy there was injury to the long thoracic nerve. The integrity of the nerve can be tested at the bedside by asking the patient to
Long thoracic nerve innervates Serratus anterior. Serratus anterior originates from outer surface of upper 8 ribs and inserts onto inferior angle and medial border of scapula. 
Actions :

It rotates the scapula to help in overhead abduction.
Steady the scapula to carry weight.
Pushing of arm forward in horizontal position.
Helps in forced inspiration.
Shrug the shoulders
Raise the arm above the head on the affected side
Touch the opposite shoulder
None of the above