What is the test for credibility in a witness testimony?

In Clifford v. Flores et al, 2004 BCSC 358, the court was faced with similar issues regarding verbal agreements and irreconcilable statements by the parties. The court stated that to determine the credibility of the witnesses, it must test their respective testimonies against the facts which are not seriously disputed and in conjunction with the preponderance of the evidence and the probabilities surrounding the events: para. 39. In assessing the witness’s credibility, I have also considered the following statement from Bradshaw v. Stenner, 2010 BCSC 1398 at para. 186: Credibility involves an assessment of the trustworthiness of a witness’ testimony based upon the veracity or sincerity of a witness and the accuracy of the evidence that the witness provides … The art of assessment involves examination of various factors such as the ability and opportunity to observe events, the firmness of his memory, the ability to resist the influence of interest to modify his recollection, whether the witness’ evidence harmonizes with independent evidence that has been accepted, whether the witness changes his testimony during direct and cross-examination, whether the witness’ testimony seems unreasonable, impossible, or unlikely, whether a witness has a motive to lie, and the demeanor of a witness generally …