Training with a partner can add an additional level of difficulty (and stress) to your training. Knowing someone is watching your shots and will be providing constructive criticism can be nerve wreck for those who are newer to shooting. Check out this Tactical Tuesday video where Steve Fisher and Mike Brickner give you some ideas on how to make the most of your partner training on the range.
Having them call out which target to shoot.
I also start talking real fast and loud as they are shooting to add a little stress to the program.
I think the best stress situation was when I was shooting and having an instructor that I highly respected watching me shoot. I have shot under extreme stress being shot at myself at the time but, this was a whole new experience for me. All I wanted to do is my absolute best. Some of the basics I have always worked on did not come into play. Mind me, I did shoot well but, I know how good I could shoot. Thus the saying, you are only as good as your worst day of shooting.
Indoor range limits “stress drill” options, but I liked one - with numbered targets my Instructor gave me an equation. I had to respond with the result hitting the proper number within 2 - 3 seconds.
Outside range gives a lot options. Best “partner” shooting I’ve ever experienced - my partner was screaming at me, pushing me and run police siren over my head during shooting while moving + emergency reloads drill. 
I also like this Tactical Tuesday’s drill. 
The ranges near me won’t allow this drill. But I’ve worked on the 5x5x5x6