What is the test for a change in custody and access order?

In Gordon v. Goertz, 1996 CanLII 191 (SCC), [1996] 2 S.C.R. 27, Madam Justice McLachlin, as she then was, summarized the law respecting an application for a change in a custody and access order at para. 49. The only issue is the best interests of the child, having regard to all the relevant circumstances relating to the child’s needs and the ability of the respective parents to satisfy them. At subparagraph 7, she stated: 7. More particularly, the judge should consider, inter alia: (a) the existing custody arrangement and relationship between the child and the custodial parent; (b) the existing access arrangement and the relationship between the child and the access parent; (c) the desirability of maximizing contact between the child and both parents; … (f) disruption to the child of a change in custody; …