I have an iron farm which contains 4 villagers and a zombie. 

The villagers are a minimum of 2 blocks away from the zombie and they also have line of sight with the zombie but don't seem to be running with panic or spawning golems at all. 

The villagers have a bed and a work station, they also have a redstone circuit that breaks line of sight every now and then but I can't seem to get iron golems to spawn.