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

Another basic principle is that the courts should only rule on a constitutional issue if a sufficient factual basis has been established to analyse the legal issue: 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. McKay v. Manitoba, 1989 CanLII 26 (SCC), [1989] 2 S.C.R. 357, at paragraph 8.