Getting tested is the best way to prevent receiving an STD. Many couples, especially ones in college have sex with a partner they are not sure has been tested for an STD. Imagine how many people your spouse has been with that also have probably not been tested.
Take a look at this scenario;
Jamie was just tested 3 months ago and did not have an STD and she has been having sex with her boyfriend (Josh) who has never been tested. Although three months ago she didn't have an STD, she now has one. The boyfriend went out to the club one night and had unprotected sex with a girl he met that night (Amy) because he was drunk. Amy has slept around with a few guys, so she has the STD also. Amy received the STD from Brandon who got it from his ex-girlfriend Britney who cheated on Brandon.
Do you see how big of a chain reaction it is when one person doesn't have safe sex and also get tested. It is like a small epidemic of an STD going around because of whoever Britney slept with. The STD being spread could have been eliminated if each person would have gotten tested.
You probably wonder how can you get your partner to get tested. You may not want to upset your partner, but I'm sure you'd rather them be upset at you then you upset at them because they gave you HIV, Chlamydia or Genital Herpes. Make sure you let your partner know you can get tested together, so that things do seem weird. They should know that you won't be judge them about their results. Also reassure them that everything stays between the two of you. No person wants their spouse's best friend knowing that they have an STD! Try to make things as easy as possible and if you all have not had sex with each other yet make that one way for you to have sex.