In all business messages, communicators should ideally aim to

Focus on a target audience, cater the message to specific age group/gender, capture attention of audience, create lasting image in audience's head using proper, effective techniques.

The advantage of administering personality tests on employees is that it will allow the employer to know the mindset and personality of the employee. this will allow the employer to at least have an idea as to how the employee works and how his attitude in the workplace. the disadvantage is that it may make the employee a little anxious as to whether he would meet the personality requirements of the employer and whether he would be able to retain the job or not.