PvP 1 Gate Robo vs 4 Gate

How well does a 1 Gate Robo work against a 4 Gate?
I know a 3 Gate Robo works really well, I guess the difference now is that you'll have a pretty small gateway army but maybe an extra Immortal?
I guess the real question is:
When a 4 Gate hits you, which units and how many units would you have and would you be able to stop the 4 Gate by 1 Gate Roboing?