The pleadings in the proceeding by mandamus are those mentioned in ORS 34.170 and 34.180, and none other are allowed. They are to have the same effect and construction, and may be amended in the same manner, as pleadings in an action. Either party may move to strike out, or be allowed to plead over after motion; and the issues joined shall be tried, and the further proceedings thereon had in like manner and with like effect as in an action.
ORS 34.190