What is the test for a court to vary a custody order?

McLachlin J. (as she then was) set out the requirements for showing a material change of circumstances at ¶13 and 15: It follows that before entering on the merits of an application to vary a custody order the judge must be satisfied of: (1) a change in the condition, means, needs or circumstances of the child and/or the ability of the parents to meet the needs of the child; (2) which materially affects the child; and (3) which was either not foreseen or could not have been reasonably contemplated by the judge who made the initial order. … The third branch of the threshold requirement of material change requires that the relocation of the custodial parent not have been within the reasonable contemplation of the judge who issued the previous order: Messier v. Delage, 1983 CanLII 31 (SCC), [1983] 2 S.C.R. 401. If a future move by the custodial parent was considered and not disallowed by the order sought to be varied, the access parent may be barred from bringing an application for variation on that ground alone. The same reasoning applies to a court-sanctioned separation agreement which contemplates a future move. In such cases, the application for variation amounts to an appeal of the original order. (emphasis added)