When I put "testfor x=7,y=5,z=32" in a command block and hooked it up to a redstone clock so that it would update itself and put a redstone comparitor in front of it...
What I expected to happen was...:
-When I was at coordinates "7 5 32", the comparitor would turn on, powering the redstone in front of it
-When I was not at said coordinates, the comparitor would turn off
What actually happened was...:
As soon as the command was entered in the command block, the comparitor turned on, and refused to turn off no matter where i was (including those coordinates)
Steps to Reproduce:
1. Place a command block
2. Place a redstone comparitor facing out from the command block
3. In the command block, type the following: "testfor @p[x=<your x coordinate>,y=<your y coordinate,z=<your z coordinate>]"
4. Place a redstone repeater facing out from the comparitor
5. Place a redstone lamp so that it gets input from the redstone repeater
6. Hook the command block up to a redstone clock (google how to do this if you don't know)
All other commands and testfor arguments work perfectly for me.
At the input of a commenter, I included a maximum search radius argument ("r=<radius>"). Now the command block acts as if the search radius argument was the only argument, turning on when I am in radius and off when I am out of radius, regardless of coordinates.