What is the test for collateral attacks?

In the C.U.P.E. decision cited above, the court wrote the following about a collateral attack: The rule against collateral attack bars actions to overturn convictions when those actions take place in the wrong forum. As stated in Wilson v. The Queen, 1983 CanLII 35 (SCC), [1983] 2 S.C.R. 594, at p. 599, the rule against collateral attack, …has long been a fundamental rule that a court order, made by a court having jurisdiction to make it, stands and is binding and conclusive unless it is set aside on appeal or lawfully quashed. It is also well settled in the authorities that such an order may not be attacked collaterally – and a collateral attack may be described as an attack made in proceedings other than those whose specific object is the reversal, variation, or nullification of the order or judgment.