I so agree with you that the real test starts after marriage. Both Yash/Pooja were all in love and infatuated with Zoya/Aditya before marriage but when they started living together and all that, that brought out the real side of each other.
In the movie Kurbaan the girl's dad had said "when people are in love, they shut all the windows of their house and only focus on each other. But once reality hits and those windows are open, love is usually the first thing to fly out."
Not in any way saying AdiYa's love will fly out, but no doubt they'll have to work hard. Zoya will have to be more thoughtful than she was with Yash and Aditya will have to be more loving than he was with Pooja.
Also let's not forget the murder mystery is still there, I feel the murder mystery track will run alongside the shaadi