What is the legal test for establishing a prima facie breach of s. 15 of the Charter of Canada?

In Law Society of British Columbia v. Andrews, 1989 CanLII 2 (SCC), [1989] 1 S.C.R. 143 at para. 31 the court stated the stringent test that must be met by claimants to establish a prima facie breach of s. 15: It is not every distinction or differentiation in treatment at law which will transgress the equality guarantees of s. 15 of the Charter. It is, of course, obvious that legislatures may – and to govern effectively – must treat different individuals and groups in different ways. Indeed, such distinctions are one of the main preoccupations of legislatures. The classifying of individuals and groups, the making of different provisions respecting such groups, the application of different rules, regulations, requirements and qualifications to different persons is necessary for the governance of modern society.