What is the test for reversal of a decision by a judge to grant a motion of appeal?

"Where, as here, a trial court has discretionary power to decide an issue, its decision will be reversed only if there has been [763 P.2d 486] a prejudicial abuse of discretion. 'To be entitled to relief on appeal ... it must clearly appear that the injury resulting from such a wrong is sufficiently grave to amount to a manifest miscarriage of justice....' [Citation.] However, 'discretion may not be exercised whimsically and, accordingly, reversal is appropriate "where no reasonable basis for the action is shown." [Citation.]' [Citations.]" (Baggett v. Gates (1982) 32 Cal.3d 128, 142-143, 185 Cal.Rptr. 232, 649 P.2d 874.)