How to test for the long thoracic nerve?

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.