What is the test for dismissing an appeal from a nonappealable order?

"It is of course fundamental that an appellate court has no appellate jurisdiction to entertain and pass upon an appeal from a nonappealable order. [Citations.] If it be determined that the appeal is from a nonappealable order and the reviewing court is without appellate jurisdiction, that court has no recourse other than to dismiss the appeal on its own motion. [Citations.]" (Efron v. Kalmanovitz (1960) 185 Cal.App.2d 149, 152.)