What is the test for commenting upon evidence at trial?

In support of this proposition, Taschereau J. cited Spencer v. Alaska Packers (1905) 1904 CanLII 23 (SCC), 35 S.C.R. 362. In that case, Nesbitt J. expressed the principle this way at 371: I do not think the judge is bound to comment upon evidence in the sense of reviewing what the several witnesses have sworn to, or to point out for consideration of the jury anything which may strike him as throwing light upon the credibility of the story, but I think he is bound to direct the jury as to the law and to direct their attention how that law is to be applied to the facts before them according as they find them.