I'm testing the use of /testfor, and under no circumstances can I get it to produce an output as intended. I've copied tutorials from YouTube as well as the example on gamepedia (http://minecraft.gamepedia.com/Tutorials/Command_Block), and it still produces a last known output of "that player cannot be found".

My desire is to have it check the nearest 2 blocks (other than itself, so r=2) for a player.

/testfor @p[r=2]

Doesn't matter if I'm standing on top of it, or standing 3+ blocks away, there is no difference in the output of the block (that player cannot be found). Also, it produces a redstone output whether or not it should have failed. I have a clock circuit with a command block in series with the command above. The circuit clocks, even if I'm standing 3+ meters away.