What is the test for credibility in a witness testimony?

" ' "Although we must ensure the evidence is reasonable, credible, and of solid value, nonetheless it is the exclusive province of the trial judge or jury to determine the credibility of a witness and the truth or falsity of the facts on which that determination depends. [Citation.] Thus, if the verdict is supported by substantial evidence, we must accord due deference to the trier of fact and not substitute our evaluation of a witness's credibility for that of the fact finder." ' " (People v. Smith, supra, 37 Cal.4th at p. 739.)