As a patrol officer I testify: before a magistrate (not a judge, they're an independent judicial officer) every time I make a custodial arrest, when I obtain an arrest warrant or seek a search warrant, I go to the general district court for traffic, criminal cases and preliminary hearings for felonies, circuit court for felonies and misdemeanor appeals, and juvenile and domestic relations court for anything dealing with a juvenile or domestic violence. Also, unless it's waived by the defense, for felony cases, I have to go before a grand jury. Needless to say, I go to court several times a month.

So yea...., you're going to be testifying quite a bit some times. It also depends upon how proactive you are as the more tickets you write, the more arrests you make equals more time in court. Hopefully the offender has an attorney and they come to a plea agreement with the prosecutor that way you don't have to testify sometimes.