What is the test for determining whether a criminal defendant has no interest in a specific term of imprisonment?

"A criminal defendant has no vested interest "in a specific term of imprisonment ...." " ( People v. Turnage (2012) 55 Cal.4th 62, 74, 144 Cal.Rptr.3d 489, 281 P.3d 464.) "[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]." ( Id. at pp. 74-75, 144 Cal.Rptr.3d 489, 281 P.3d 464.)