Mate of mine had fresh engine built, didn't run right, turned out the piston rings supplied were slightly the wrong size...
other than that, my fav:
https://mobiloil.com/en/article/car-maintenance/car-maintenance-archive/how-to-do-a-leakdown-test
I've got one of their end cans, quality is good and solid. Price may be cheaper 'cos they don't seem to advertise aggresively so must be able to keep costs dow. Phone them up and speak to them... that's what I did.