All commissioned officers shall be appointed by the Governor and be commissioned according to the rank in the arm or service in which they are appointed. They shall meet all the requirements and qualifications now or hereafter prescribed by the laws of the United States and the rules and regulations promulgated thereunder for the organization and regulation of the Pennsylvania National Guard. No officer shall be commissioned until he shall have successfully passed such tests as to his physical, moral and professional fitness as shall be prescribed in relation thereto.