When any suit is brought against two or more defendants upon any contract, any one or more of the defendants being surety for the other, the surety may cause the question of suretyship to be tried and determined upon the issue made for the parties defendant at the trial of the cause, or at any time before or after the trial or at a subsequent term. Such proceedings shall not delay the suit of the plaintiff.
Tex. R. Civ. P. 32