What is the test for dismissing an appeal from a lower court?

"`"As a general rule, `an appeal presenting only abstract or academic questions is subject to dismissal as moot.' [Citation.]" [Citation.]' [Citation.] `"When no effective relief can be granted, an appeal is moot and will be dismissed." [Citations.]' [Citations.] `"`It necessarily follows that when, pending an appeal from the judgment of a lower court, and without any fault of the defendant, an event occurs which renders it impossible for this court, if it should decide the case in favor of plaintiff, to grant him any effectual relief whatever, the court will not proceed to a formal judgment, but will dismiss the appeal.'" [Citations.]' [Citations.]" (People v. Travis (2006) 139 Cal.App.4th 1271, 1280.)