What is the test for dismissing an appeal?

We agree with the People that the appeal is moot. "'[A]n action that originally was based on a justiciable controversy cannot be maintained on appeal if all the questions have become moot by subsequent acts or events. A reversal in such a case would be without practical effect, and the appeal will therefore be dismissed.'" (People v. Herrera (2006) 136 Cal.App.4th 1191, 1198; accord, People v. DeLeon (2017) 3 Cal.5th 640, 645 ["'"[W]hen, pending an appeal from the judgment of a lower court, and without any fault of the [opposing party], an event occurs which renders it impossible for this court, if it should decide the case in favor of [defendant], to grant him any effectual relief whatever, the court will not proceed to a formal judgment, but will dismiss the appeal"' as moot."].)