With the emergence of psychometric testing and assessment days being used by more and more by companies, does someone have the recipe of success?

With psychometric testing, companies try to identify certain traits and behaviours within an individual that would go some way to identifying what they would be like if they employed that candidate. Are there different tendencies for each role? Are Sales Executives more extroverted than a technician for example? I know technicians that have also been very successful in sales!

Are generic testing patterns for certain roles the best way to judge who will and who will not be suitable for certain types of roles? With no 'right' or 'wrong' answers to these tests, how do some people perform in them consistently better than others? Having taken a few of these tests previously myself with varying results, does your mood at the time of taking the tests have a big impact on how you perform and the results that are gleaned from them?

I am not sure there is a predetermined approach to who will and will not be successful in any given role but meeting people and getting to understand them as an individual must surely be more of an indicator of how someone will perform in a job role?