I usually check my pH about 5-10 minutes after mashing in to give things time to come to equilibrium but soon enough that I can make adjustments if I need to. I don't know what you mean by "Right before I add the test?"
You don't need to worry about pH for an extract brew. pH of the mash affects the ability of the enzymes in the grain to convert the starches to fermentable sugars, but that's not an issue for extract.