Parties to be admissible witnesses

On the trial of any issue joined, or of any matter or question, or on any inquiry arising in any suit, action or other civil proceeding in any court, the parties thereto, and the persons in whose behalf any such suit, action or other civil proceeding may be brought or defended shall, except as hereinafter provided, be competent and compellable to give evidence, either viva voce or by deposition or affidavit according to the practice of the court, on behalf of either or any of the parties to the said suit, action or other civil proceeding.