push rod ?

Yup the pushrod length and sweep test are usually performed at the same time.
We use the adjustable pushrod. And we need to prevent the hydraulic lifter from bleeding down. First, on the cylinder we are going to check,the valve springs are removed, and much softer checking springs are installed.Alternatively(cause I hate RnRing springs) a Checking Lifter can be made up. This is nothing more than a matching lifter with the guts removed and a spacer made up and installed under the cup to simulate the preload you are wanting to run.I built mine decades ago.After all these years maybe somebody is making these.
As to preload,most guys run about .020 to .040. I have adjustable rockers so run just barely enough to keep things quiet.Then at some higher rpm those lifters may pump up and go solid. If/when they do, its no biggy. I get a rough idle for a couple of seconds, but no internal damage. But,when running non-adjustables its better to run closer to .040inch preload, so the lifters will stay quiet for the life of the lobes.
Once the set-up is ready, you put the cam on the base circle, and install your adjustable push rod, and lengthen it to zero lash. Then you do the sweep-test, to see where youre at.If that comes out 100%, then you simply measure that pushrod and record the number and its location. Then you repeat the test on the other valve, and record the measurement and location.
Now if the heads or decks have been milled its a good idea to measure at least one valve at each corner.Then average the corner measurements out. If things get too close to the minimum, you may have to make a judgement call, and arbitrarily add some preload. Otherwise one day your engine will develop a lifter-tick.
Finally you evaluate the numbers,and order the correct one-size-fits-all pushrods.
In a heavily machined combo the ideal pushrod lengths might be all over the place.In this case it might be preferable to run adjustables in every single location.With modern equipment, machining is much more precise than in years gone by, and it would be a sad day if you had to put adjustables in every location,today.