What is the test for retroactive aid in the context of retroactive disability benefits?

This argument rests upon a premise which appellant states in this language: '. . . (T)he many factors which influence an individual's eligibility will have to be evaluated in each case in order to determine the propriety of retroactive aid. Many of the individuals who were either denied (AFDC) benefits or had benefits terminated on the basis of the subject regulation may also have been ineligible for a myriad of other factors. In other words, while the invalidity of the regulation may be a fact common to all, the right to retroactive aid 'can be established only after extensive examination of the circumstances surrounding each party. '' (Appellant here quotes and relies upon City of San Jose v. Superior Court, supra, 12 Cal.3d 447 at p. 461, 115 Cal.Rptr. 797, 525 P.2d 701.)