If the police pull you over and they suspect you've been drinking and are driving under the influence and you refuse to take a Breathalyzer test in Massachusetts or any other state then what will most likely happen is you'll get arrested.
Once you get arrested they will take you to jail and then the DUI test will be done there whether through taking the breathalyzer test at jail or through a urine or blood sample.
You will eventually get tested someway so it's best to just go along with what the police want and make it easier on yourself.