A 1ml syringe is a handy tool (as opposed to an eye dropper) to initially get a rough feel for tipper operation, then feed a measured amount of water (measured using graduated glass cylinder) through the gauge and initially multiple runs at varying time spans trying to emulate the most appropriate rain rate. As a home made dripper, a garden variety adjustable irrigation dripper works fine. What I use as a counter to count the tips is an old WMII console.
For a 0.2mm tipper I run 425ml and top off the last tip with a syringe then compute the adjustment noting that you shouldn't adjust the whole adjustment if it is large as the dynamics of the tipper will change and you will get an over adjustment. If you require say a 18% adjustment (not uncommon) then go maybe 2 full turns of the screws then run the test again.