(forgive my sloppy writing, I jump from 1st to 3rd person and from present tense to past tense.... but you'll get the idea).
I want to start this off by saying I understand why art tests are given, and that my perspective is somewhat limited. But there are some principles here that I think we can all agree on.
I have done art tests for games and animation. None of these landed a job, and it is fair to say I wasn't what they were looking for. Beyond that is speculation and it is challenging to be objective about it.
I understand (as I think most artists do) that art tests are a useful tool for art directors to help find the best qualified, or at least the best fit, for a position. What I don't understand is why these tests are free? Let me rephrase as that was rhetorical. Tests are free because people will do it for free and the community of artists are chalk full of suckers, myself included. I'm just going to list off the problems I have with the process. These may or may not be representative of the majority so take it for what it is.
1.) Probably the worst offense and most common is the time consuming and long test. I did a test for a large studio that is known world wide. It was a huge test involving a character, guns, and props, all of which required turns left, right, top, bottom, front and back and even work out the mechanics of one of the gun concepts. It was obvious they needed these turns for the Korean studios that only do what you ask. Unless your a masochist you probably find turns tedious. This test took me a week. I'm not an art director, but if I was, I'm confident it would not take more than 1 object or character test to know if that person will work or not, However I am not. The point is I did a week of work with nothing to show for it because of the NDA, I can't use the work in my portfolio, so a complete waste of time for me.
2.) Minimum wage. That's all it takes. It doesn't matter if the studio will or will not use your work. Work deserves compensation if it serves a function. Oh how nice it would be if you could test your electrician or your dentist for free, rejecting them because you didn't like the temperature of the office and the staff wasn't very polite (lets not get into how this isn't economically comparable). Paying for a test is reasonable, it would not take a significant amount of the studios budget. It will also encourage both parties to be a little more attentive.
3.) Vague tests. What do they want? Are they testing me if I'll ask questions or how well I can interpret the Art directors vision? Now someone may say, "Obviously you ask for clarification", but that is hardly the point. If you want to know if I'm a good fit, interview me, if you want to see if I can do the job ask for something specific and tell me exactly what you expect. From the artist's perspective it is REALLY hard to put your best effort into a test knowing the high chance you won't be considered. Call it pessimism or a self fulfilling prophecy but I guarantee a test is not going to be representative of their ability because it's not worth their time.
4.) Most jobs have a 90 day probation period. There are also short contracts, job for hire, project hire, freelance and nuances in between. If you're savvy Art director, you will probably get more out of an interview than a test, but I'm not going to get into interviews. What I'm saying is, we have enough hoops to jump through for an insecure job. This is just one more.
5.) Testing when the artist isn't a good fit anyway. Maybe it's to give someone a chance, I don't know. But I have friends, and even myself who have tested on things that were absolutely a horrible fit. Now I certainly share some of the blame for applying for a position where my style (cartoony?) will not work for a hybrid realism horror game. So why did the art director waste my time giving a test? I think what is going on is rather than go through each portfolio it is easier to flip through tests. Of course this is speculation but I'm certain some studios do this.
6.) The NDA (Non-Disclosure Agreement). I don't own my work, I can't show my work, I can't talk about the test (except I do). I get projects must be kept secret, but when you are not compensated in any way, this is the final insult. Whether or not they use the work, they have the OPTION to do so.
I have had my test used on a product. I'm not going to say who and where on Facebook because of the NDA and because of the that is a serious accusation, but in that particular situation I didn't even get the courtesy of a rejection email, just silence, even after several followups.
The jobs I've had, have not required tests, they liked my portfolio, they liked me at the interview, and I delivered them quality art.
Personally, I will never test for anything more than a short style test, less than half a day's worth of work, Even the best have done those. Anything more and I want to be paid, because that art director (or whoever) is stepping out of line. The point is, I don't work for free, period. Neither should you. Before anyone talks about the studios needs or their budget and how it's frustrating to hire someone who then doesn't deliver, consider the needs of an artist to put food on the table and make rent. Competition this way is a race to the bottom. Just don't participate, other opportunities will come.