Any filter will weed out some percentage of good people. The question is really in the caveat, whether you are doing so unnecessarily. That depends on the resources available to your search and the position you are trying to fill, among other factors. Personally, I don't mind taking the odd test, though I find it a bit grade-schoolish when potential employers call it a test. I've always called such "technical evaluations" when interviewing candidates (six of one, I know), and made sure that (1) the questions were interesting to the candidate, and (2) that the candidate clearly understood the questions were intended to elicit insight into their thinking rather than grade spot performance. The former of those reflects another aspect of a search, one that I feel is more important than test/don't-test, and that is Accurate Position Description. Almost every job posting I read asks for qualifications that, if satisfied, would put the rest of the workforce to shame. Focus on what technical aspects the position should fulfill, rather than listing ridiculous qualifications and proficiency in a cadre of technologies in the hopes of hiring the "perfect" person. (I once read an advertisement for a position that required 20 years of professional Java development experience. Think about it.) There is rarely a perfect person. Decide what the focus of the position is, advertise for that, and ask interesting questions within the focus in order to evaluate capability. My two cents.