There are two separate things:
Shock Tuning
Car Testing
Barstow is the best (except San Filipe) for tuning shocks. For a pre race shakedown I sometimes went to closer areas. In my neck of the woods we used Apache Canyon or Quatal Canyon, even Balanger canyon a few times. We’d make sure it ran good, and everything worked, But if you’re gonna try different springs, change shim stacks back and forth and optimize the suspension Barstow is the place. I usually tuned at Barstow Start/finish, then I found some chop like over by Hodge to make sure the whoop tune didn’t F up the handling in the chop. And it usually did.