But in a playtest, where you're basically testing rules in a series of set encounters with minimal story, it's a little harder. Heck, it's often better to just not even worry about whether the players are "into it." You're there to do a job, after all. But I don't have as much fun if the players aren't into it. And I didn't have the chance to set up the kinds of antagonistic relationships with villains, set up giant battles (since the encounters are pre-set), or even spring extra villains on the characters when they're least expecting it.
So I settled for outright antagonism. Sure, it's a kludgy tool, but you gotta work with what you have. By making the players think you're out to get them, you get some of that fun dramatic tension in every fight. Every spell or sword swing from an enemy feels personal, and victory is all the sweeter as a result. I wouldn't do this week after week in a real campaign -- or at least, I wouldn't do it with such a heavy hand. But it's fun for a playtest, and the players are responding. I even have moles planted in their midst, stirring the pot and spreading the fear like a virus. Good times.