What is the test for credibility in the context of a finding of insufficient evidence in a personal injury case?

At the outset, it bears mention that "(i)n resolving the issue of the sufficiency of the evidence, we are bound by the established rules of appellate review that all factual matters will be viewed most favorably to the prevailing party (citations) and in support of the judgment (citation). All issues of credibility are likewise within the province of the trier of fact. (Citation.) 'In brief, the appellate court ordinarily looks only at the evidence supporting the successful party, and disregards the contrary showing.' (Citation.) All conflicts, therefore, must be resolved in favor of the respondent. (Citation.)" (Nestle v. City of Santa Monica (1972) 6 Cal.3d 920, 925-926, 101 Cal.Rptr. 568, 496 P.2d 480.)