What is the test for "rational basis review" in the context of equal protection legislation?

"Where, as here, a statute involves neither a suspect class nor a fundamental right, it need only meet minimum equal protection standards, and survive 'rational basis review.' [Citation.]" (People v. Turnage (2012) 55 Cal.4th 62, 74.) "[E]qual protection of the law is denied only where there is no 'rational relationship between the disparity of treatment and some legitimate governmental purpose.' [Citation.] In other words, the legislation survives constitutional scrutiny as long as there is ' "any reasonably conceivable state of facts that could provide a rational basis for the classification." ' [Citation.] This standard of rationality does not depend upon whether lawmakers ever actually articulated the purpose they sought to achieve. Nor must the underlying rationale be empirically substantiated. [Citation.] While the realities of the subject matter cannot be completely ignored [citation], a court may engage in ' "rational speculation" ' as to the justifications for the legislative choice. [Citation.] It is immaterial for rational basis review 'whether or not' any such speculation has 'a foundation in the record.' [Citations.]" (Id. at pp. 74-75.)