I think it's pretty clear to all involved that the current system of test screenings really doesn't result in the most artistically rewarding film. The studio ushers in a bunch of people who fit the demographic range they would like to sell the film in question to, then adjust the film to try to appeal to as many people in the audience as possible. I'm not saying this process is always bad. If nothing else, it tells a studio that they shouldn't even bother trying to sucker people into seeing something truly horrible like Lost Souls or Slackers, giving them free reign to do a one-week release in February when only teenagers desparate to get out of the house will see it.
All this isn't to say you couldn't do a valid test screening - one that might actually help the filmmakers make a genuinely better film. Find some people who generally like the works of the screenwriter and director, people who like the genre in question, people who clearly understand what it is they're going for. Had they done such a test screening for Happy Campers, I like to think I'd have been in the test...
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