What tests (beside TB test) and vaccinations are needed before starting first time remicade (infliximab) fusion for left-sided ulcerative colitis? Mmr vaccine?

Check hepatitis B. The risk of reactivation of tuberculosis and hepatitis b when taking Remicade (infliximab) obligates pre-treatment testing. Live vaccines can not be accepted while on the drug. Your doctor will no doubt be candid when discussing all the risks of "biologic treatment"--please discuss these with him before initiating this very efficacious and generally well-tolerated drug class.
All vaccines and HBV. Hbv status needs to be determined and vaccination recommended as needed. If you are in need of any liver vaccines make sure that occurs before you start ifx. Otherwise follow standard vaccine recommendations including influenza (yearly) and pneumococcus.
Immunsuppression. Check in with your gastroenterologist. Remicade (infliximab) works really well for ulcerative colitis, by selective immunsuppression. Meaning lowering your immune system. So your GI and primary docs want to check you for chronic low lying infections that could become more aggressive when your immune system is depressed. Tb, cmv, hepatitis c and b and some others depending on your history and exposures.