Put the summary of the bug you're having here
----------
the testfor command isn't working (on servers)

What I expected to happen was...:
Describe what you thought should happen here
----------
The comparator to light up and send out a redstone pulse

What actually happened was...:
Describe what happened here
----------
The comparator did nothing didnt light up or send out a pulse

Steps to Reproduce:
1. Make sure you are on a 13w39b server
2. using scoreboard set up a objective (i used dummy)
3. set up a redstone clock going into a command block
4. put /testfor @p[ score_OBJECTIVESNAME_min=1,score_OBJECTIVENAME=1 ] in the command block (there is a space in the command with the [ ] because it will turn it into a link if i dont have th space
5. place comparator on the other side of the command block
6. turn on the redstone clock