What is the test for awarding costs to the successful litigant?

First, one of the basic rationales for awarding costs to the successful litigant is to encourage the settlement of disputes: Min. of Forests v. Okanagan I.B., supra, at 274, 275 (W.W.R.) (paras. 22, 26). Competing parents often estimate their possible expenses and rewards before deciding to fight, settle, or surrender. Therefore, one cannot calculate a costs régime without seeing how the parents would so estimate if they thought rationally.