What is the test for calculating damages for a plaintiff's failure to mitigate her losses?

Our Court of Appeal upheld the trial judge’s findings in O’Brien v. Cochrane, 2002 NLCA 45 and stated the method trial judges must follow to assess the impact on damages of a plaintiff’s failure to mitigate her losses: Thus, a court must estimate the value of the chance that the treatment would have eliminated or reduced the plaintiff's loss. It is wrong for a court to find that because, on the balance of probabilities, the treatment would have succeeded, the plaintiff is entitled to nothing for her loss. This method of reducing damages for the chance that the plaintiff might have mitigated is used in ordinary commercial cases as well and is consistent with the measurement of future damages”: O’Brien v. Cochrane, paragraph 25.