To any lift really.

So the spring will have some rating for @seat and specific lift (spring compression) given the particular spring rate. If you want to check whether the spring still holds true to those values (assuming of course that you did that check already to start off with when you originally installed the springs) then yeah, simply push down on the rocker arm until the valve shows the desired lift and read off the pressure the tool is seeing.

I find that tool to be the quickest way to actually check the "health" of the valvespring fairly quickly (stll installed, all you need to do is to yank the valve cover off and go measuring).

Realistically speaking, as you get into more aggresive springs (and therefore higher spring rates) it's much easier to check @seat and maybe half-lift...ha ha, the arm sure gets a pretty good workout. I only did this a couple of times, so I suspect that the engine builders on here probably have much more robust and easier/better ways of accomplishing the same thing.