Expert Q & A Answers About STD partner testing

I don’t have any STDs and my partner says he’s clean...should he still get tested?

I had a medical exam with my gynecologist not too long ago and everything went well, so it’s safe to say that I have no diseases. A guy whom I currently see has never been tested for any sexual diseases, and he says he doesn’t have any. I trust him, but I don’t trust the other people he has been with. Is it necessary for him to get tested, too? Do we need to use condoms?