What is the test for a remedy for unjust enrichment?

It is well to remember that both sought a remedy for unjust enrichment and to recall at the outset of the consideration of their claims this cautionary comment by Madam Justice McLachlin, writing for the majority in Peter v. Beblow, 1993 CanLII 126 (SCC), [1993] 1 S.C.R. 980 at 988, 77 B.C.L.R. (2d) 1, 44 R.F.L. (3d) 329 [cited to S.C.R.]: There is a tendency on the part of some to view the action for unjust enrichment as a device for doing whatever may seem fair between the parties. In the rush to substantive justice, the principles are sometimes forgotten. ... On the remedies side, the requirements of the special proprietary remedy of constructive trust are sometimes minimized. ... Occasionally the remedial notion of constructive trust is even conflated with unjust enrichment itself, as though where one is found the other must follow.