What is the legal test used by the courts to determine whether a local authority has acted arbitrarily or capriciously in its jurisdiction?

13 If the local agency's action is legislative in nature, then an "arbitrary or capricious" standard is used (Code Civ.Proc. 1085). If the action taken was quasi-judicial in nature, then either the independent judgment rule (for cases involving fundamental, vested rights) or the substantial evidence test will be used by the trial court (Code Civ.Proc. 1094.5). (Mountain Defense League v. Board of Supervisors, supra, 65 Cal.App.3d at pp. 727-728, 135 Cal.Rptr. 588.) However, "Where ... an agency in two capacities is simultaneously disposing of two legally required functions with but one decision, review of that determination must be by the more stringent standard." (Id. at p. 729, 135 Cal.Rptr. 588.)