How is the court in Canada assessing credibility?

There are many cases discussing how the court goes about assessing credibility. One of the best and most concise summaries of the applicable principles can be found in Gichuru v. Smith, 2013 BCSC 895 at paras. 129 and 130, aff’d 2014 BCCA 414:

The art of assessment of credibility involves examination of various factors such as: the witness’s ability and opportunity to observe events; the firmness of the witness’s memory; the witness’s ability to resist the influence of interest to modify his or her recollection; whether the witness's evidence harmonizes with independent evidence that has been accepted; whether the witness changes his or her testimony during direct and cross-examination; whether the witness's testimony seems unreasonable, impossible, or unlikely; whether a witness has a motive to lie; and the demeanour of a witness generally. See Bradshaw v. Stenner, 2010 BCSC 1398, at para. 186, aff’d 2012 BCCA 296.

Moreover, the assessment of a witness’s credibility must reasonably subject the witness’s story to an examination of its consistency with the probabilities of the surrounding conditions or circumstances. The real test of the truth of the story of a witness in such a case must be its harmony with the preponderance of the probabilities which a practical and informed person would readily recognize as reasonable in that place and in those circumstances. See Faryna v. Chorny, 1951 CanLII 252 (BC CA), [1952] 2 D.L.R. 354 (B.C.C.A.), at pp. 356-357. [Emphasis added.]