What is the test for the constitutionality of forced labor under the Thirteenth Amendment?

In Jobson v. Henne, 355 F.2d 129, 132 (2d Cir.1966), we suggested that the constitutionality of forced labor turns, in large measure, on the nature and amount of the work demanded, and the purpose for which it is required. Thus, while the Thirteenth Amendment does not foreclose the ability of the state to require chores of its institutionalized mental patients, we have recognized that "there may be some mandatory programs so ruthless in the amount of work demanded, and in the conditions under which the work must be performed, and thus so devoid of therapeutic purpose, that a court justifiably could conclude that the [work constituted] ... involuntary servitude." Id.