What is the test for determining who is the prevailing party in a personal injury action?

After determining who is the prevailing party a court must fix the amount of attorney fees. "'"Trial judges are entrusted with this discretionary determination because they are in the best position to assess the value of the professional services rendered in their courts."'" (McKenzie v. Ford Motor Co. (2015) 238 Cal.App.4th 695, 703.) We will not reverse a fee award unless it is "'"clearly wrong."'" (Id. at p. 704.) "Indulging all inferences in favor of the trial court's order, as we are required to do, we presume the trial court's attorney fees award is correct." (Ibid.)