What is the standard of review applied by a motions judge to a discretionary order of a prothonotary?

The test established by the case law that applies when reviewing a discretionary decision of a prothonotary was laid down by MacGuigan J.A., writing for the majority in Canada v. Aqua-Gem Investments Ltd., 1993 CanLII 2939 (FCA), [1993] 2 F.C. 425 (F.C.A.), who stated at pages 462 and 463: Page: 2 I also agree with the Chief Justice in part as to the standard of review to be applied by a motions judge to a discretionary decision of a prothonotary ... discretionary orders of prothonotaries ought not to be disturbed on appeal to a judge unless: (a) they are clearly wrong, in the sense that the exercise of discretion by the prothonotary was based upon a wrong principle or upon a misapprehension of the facts, or (b) in making them, the prothonotary improperly exercised his discretion on a question vital to the final issue of the case. Where such discretionary orders are clearly wrong in that the prothonotary has fallen into error of law (a concept in which I include a discretion based upon a wrong principle or upon a misapprehension of the facts), or where they raise questions vital to the final issue of the case, a judge ought to exercise his own discretion de novo.