What is mootness and what is the test for mootness?

The doctrine of mootness was described by Sopinka J. for a unanimous court in Borowski v. Canada (Attorney General), 1989 CanLII 123 (SCC), [1989] 1 S.C.R. 342 at 353 as follows: The doctrine of mootness is an aspect of a general policy or practice that a court may decline to decide a case which raises merely a hypothetical or abstract question. The general principle applies when the decision of the court will not have the effect of resolving some controversy which affects or may affect the rights of the parties. If the decision of the court will have no practical effect on such rights, the court will decline to decide the case. This essential ingredient must be present not only when the action or proceeding is commenced but at the time when the court is called upon to reach a decision. Accordingly if, subsequent to the initiation of the action or proceeding, events occur which affect the relationship of the parties so that no present live controversy exists which affects the rights of the parties, the case is said to be moot. … The approach in recent cases involves a two-step analysis. First it is necessary to determine whether the required tangible and concrete dispute has disappeared and the issues have become academic. Second, if the response to the first question is affirmative, it is necessary to decide if the court should exercise its discretion to hear the case. ...In the interest of clarity, I consider that a case is moot if it fails to meet the "live controversy" test. A court may nonetheless elect to address a moot issue if the circumstances warrant.

There may be circumstances under which a court may exercise its discretion to hear a case, notwithstanding that it is moot. Sopinka J. identified three basic rationale to consider. These were summarized recently by Garson J.A. in Binnersley v. BCSPCA, 2016 BCCA 259: