Why wont /testfor work?
I've been trying to do /testfor @a [r=5] for something, but it wont work! It just gives me an error message like "Data tag" something something "Unexpected "[" as first char." I've done the command before and it works, so why won't it work now??
Once again, you have put a space in between the @a and the radius selector.
Correct command: /testfor @a[r=5]
A redstone comparator coming out of the block will emit a signal when this is true.