Tex. Civil Practice and Remedies Code § 15.064: HEARINGS.

(a) In all venue hearings, no factual proof concerning the merits of the case shall be required to establish venue. The court shall determine venue questions from the pleadings and affidavits. No interlocutory appeal shall lie from the determination.

(b) On appeal from the trial on the merits, if venue was improper it shall in no event be harmless error and shall be reversible error. In determining whether venue was or was not proper, the appellate court shall consider the entire record, including the trial on the merits.

Acts 1985, 69th Leg., ch. 959, Sec. 1, eff. Sept. 1, 1985.