What is the test for a presumption in favour of the custodial parent in a custody matter?

Gordon v. Goertz holds against a presumption in favour of the custodial parent, providing some further direction as follows: 46 Finally, the proposed presumption in favour of the custodial parent may be criticized on the ground that it tends to shift the focus from the best interests of the child to the interests of the parents. … The child’s best interest must be found within the practical context of the reality of the parents’ lives and circumstances, one aspect of which may involve relocation. But to begin from the premise that one parent has the prima facie right to take the child where he or she wishes may unduly deflect the focus from the child to its parents. 48 While a legal presumption in favour of the custodial parent must be rejected, the views of the custodial parent, who lives with the child and is charged with making decisions in its interest on a day-to-day basis, are entitled to great respect and the most serious consideration. The decision of the custodial parent to live and work where he or she chooses is likewise entitled to respect, barring an improper motive reflecting adversely on the custodial parent's parenting ability. 50 In the end, the importance of the child remaining with the parent to whose custody it has become accustomed in the new location must be weighed against the continuance of full contact with the child’s access parent, its extended family and its community. The ultimate question in every case is this: what is in the best interests of the child in all the circumstances, old as well as new?