What is the test for establishing a factual basis in Charter cases?

In the case MacKay v. Manitoba, 1989 CanLII 26 (SCC), [1989] 6 W.W.R. 351; 99 N.R. 116 (S.C.C.), the court as a preliminary matter had to make a determination as to whether there is sufficient evidence presented to enable the court to consider the Charter issues raised by the appellants. In that case the court stated that the onus lies upon the litigants to provide the court with an evidentiary foundation to substantiate the breach. Cory, J., at p. 354 states: "Charter cases will frequently be concerned with concepts and principles that are of fundamental importance to Canadian society. For example, issues pertaining to freedom of religion, freedom of expression and the right to life, liberty and the security of the individual will have to be considered by the courts. Decisions on these issues must be carefully considered as they will profoundly affect the lives of Canadians and all residents of Canada. In light of the importance and the impact that these decisions may have in the future, the courts have every right to expect and indeed to insist upon the careful preparation and presentation of a factual basis in most Charter cases. The relevant facts put forward may cover a wide spectrum dealing with scientific, social, economic and political aspects. Often expert opinion as to the future impact of the impugned legislation and the result of the possible decisions pertaining to it may be of great assistance to the courts. "Charter decisions should not and must not be made in a factual vacuum. To attempt to do so would trivialize the Charter and inevitably result in ill-considered opinions. The presentation of facts is not, as stated by the respondent, a mere technicality rather, it is essential to a proper consideration of Charter issues. A respondent cannot, by simply consenting to dispense with the factual background, require or expect a court to deal with an issue such as this in a factual void. Charter decisions cannot be based upon the unsupported hypotheses of enthusiastic counsel."