What is the test for determining whether a plaintiff is entitled to sue for damages under Code of Civil Procedure section 1021.5?

In making a decision under Code of Civil Procedure section 1021.5, the trial court "must realistically assess the litigation and determine from a practical perspective whether the action: '(1) served to vindicate an important public right; (2) conferred a significant benefit on the general public or a large class of persons; and (3) imposed a financial burden on plaintiffs which was out of proportion to their individual stake in the matter. [Citations.]' [Citation.]" (Christward Ministry v. County of San Diego, supra, 13 Cal.App.4th at pp. 49-50, 16 Cal.Rptr.2d 435.) "The public always derives a 'benefit' when illegal private or public conduct is rectified, but in order to determine whether a 'significant' benefit has been conferred, the court must determine both the significance of the benefit and the size of the class receiving benefit, from a realistic assessment, in light of all the pertinent circumstances of the gains which have resulted in the particular case. [Citation.]" (Id. at p. 50, 16 Cal.Rptr.2d 435.)