The name of the movie where a couple are faking a marriage?

I watched this one a long time ago,I'm thinking it was done in the
60's. I believe they lived in an apartment and they pretty much would
torture each other (note its a romantic comedy so in the end I believe
they lived happily ever after). Sorry if I'm a bit sketch on the
details I only saw the movie once a very long time ago. Does any of
this ring any bells for anyone?