Random testing is one the method of keeping a check on drug abuse by the employees of an organization under which any employee can be tested randomly on any day or time. But the number of times a particular person can be tested is specified by stating the time period, for example maximum one random test in a month.
An organization can carry out a random drug test only if this clause has been mentioned in its policies regarding the drug testing of its employees.
Random drug testing is to promote a drug-free and safe workplace and is usually ordered to be carried out when the employer has an evidence or reason to believe that a particular employee is engaged in drug abusing. This happens when any colleague complains to the employer or the employer suspect uncommon employee behavior or if the employee was engaged in an accident during work hours.
Most of the companies have started including this clause in their employee policies, especially companies which has employees engaged in physical labor or long working hours. This ensures that the employees are not very casual until the fixed dates of drug tests are near, but instead are alert about the issue entire time.