Taking test is one of the method of testing for the job. It has both pro and cons.
There are various kind of test, it may be task related or IQ related which will give the idea about the candidate presence of mind and knowledge.
Taking test is an easy task as this test is equally placed before every candidate
General tests helps in scrutiny of the candidate
It checks the subject matter information within the candidate
Test paper if made to check the candidate potential in general, then it is good approach
Eg If for a job profile for marketing guys tast are being conducted which checks his credibility for marketing skills or general aptitude, then it is good but if he being questioned on finance then it will not work.
Test can’t be a judgmental picture for candidate
Candidate can’t be judged on the basis of test only
Even if the test is related to some specific role, it does not justified the real knowledge of the candidate.
E.g if a sales guy being asked sales related question and he failed but still he could be a very good sales person.