Ok, I totally misunderstood your test.
I thougth I was trying to get a GPM where there was no draw down at all, but I guess there is always some.
If I'm going to use this well to supplement my pond level, there will be a sumbmersible in it running 24/7, at whatever GPM the well can replenish. I do not live at this property, so I will not be there to keep an eye on this well pump.
So I guess I have to think about this some more, because the only pumps that will work to do the test are the expensive ones. And I don't want to just go buy a 3 GPM submerssible. I need to maximize the GPM I get out of this well. If I buy a 3 GPM pump and it works fine and can run continuously, I'll always be wondering how much GPM I could have had. 4, 5, 6 or more? etc...