I believe that many benefits can come from testing workers for drug abuse. The company that employs the workers would benefit, as it would ensure that the absenteeism is low, productivity is high and injuries do not occur as often. The employee would benefit too because it would monitor the person's health and ensure that they have access to help when needed.
Everyone should be tested in the workplace in order to be able to access these benefits. It would also lead to equality in the workplace. When people test positive for drugs, they should be provided with information and access to help so that they can recover. This would benefit the company as well, because it would represent an investment on its human assets.