Is it possible to do fertility test before marriage?

Sure, but...: It may be self-pay because it is not the typical way to do things (people usually don't do this). First, a couple can't really confirm they are fertile until after they deliver their first baby. The man can go pay for a semen analysis, and the woman can get a Ob-Gyn consultation... to check if they are likely to be fertile. They can do their genetics screening too, to check for major mutations.