What is the test for a reasonable decision?

A reasonable decision has been identified by Iacobucci J. in Law Society of New Brunswick v. Ryan, 2003 SCC 20, [2003] 1 S.C.R. 247, at paras. 47 and 55: 47. ... The standard of reasonableness basically involves asking "After a somewhat probing examination, can the reasons given, when taken as a whole, support the decision?" ... it requires that the reviewing court assess whether a decision is basically supported by the reasoning of the tribunal or decision-maker, rather than inviting the court to engage de novo in its own reasoning on the matter. ... . . . 55. A decision will be unreasonable only if there is no line of analysis within the given reasons that could reasonably lead the tribunal from the evidence before it to the conclusion at which it arrived. … This means that a decision may satisfy the reasonableness standard if it is supported by a tenable explanation even if this explanation is not one that the reviewing court finds compelling….