Your attorney can help you answer those questions, if necessary. Generally, you cannot know for certain. Mass. criminal procedure rule 6 covers arrest warrants – the Superior court can issue an arrest warrant. That warrant must be "signed" by the issuing official, will have the name or other reasonable means of identifying the subject, and the offense charged. An electronic signature is a signature. If the arresting officer does not have the warrant at the time of arrest, the arrest may proceed anyhow, and if he has the warrant, he shall on request show it to the defendant as soon as possible. If the officer does not have the warrant on him, he shall inform the defendant that a warrant has been issued.
There is no practical way to look at a warrant and determine that is is a real warrant as opposed to a fake document created by thugs. There is no statute under which a person can resist arrest until they are satisfied that the arrest is by a legitimate officer and that the document was properly issued by the court. If there was no proper warrant, the arrest will probably be found unlawful and you will be set free until a proper warrant is issued. It would be unlawful for thugs to take you (impersonating an officer is a crime), and that is as far as the law goes.
Ch. 267 of Massachusetts General Laws lays out the law regarding warrants, and those laws focus on the conditions for legally issuing a warrant, not for convincing a person that a warrant, search or arrest is legitimate. You may certainly attempt to confirm that the warrant and officer are real, but you cannot resist the search or arrest if you are not satisfied.