You need to give a programmer a task, then let him get back to you in a day or two. Give him something that you can't find a solution to on Google, but isn't so hard that it couldn't be done in an hour or two.

Sitting there putting pressure on the programmer working is just a prick move. If you gave the same test to a carpenter and asked him to build a bird house and the outcome would decide whether he could pay rent this month, he would cut his damn hand off. Guaranteed.