What is the test for a trade union representative action?

Following Ginter v. Gardon, supra, the court must be satisfied of the following: (i) that there is a proper cause of action; (ii) that the claims to be advanced raise common issues; (iii) that a representative action is the preferable procedure for the determination of the common issues; and (iv) that the proposed representative plaintiff(s) would fairly represent the interests of the members of the trade union and does not have any interest in conflict with those interests?