Texas Estates Code - EST § 256.156. Proof of Will Not Produced in Court

(1) the cause of the nonproduction of a will not produced in court must be proved, which must be sufficient to satisfy the court that the will cannot by any reasonable diligence be produced; and

(2) the contents of the will must be substantially proved by the testimony of a credible witness who has read either the original or a copy of the will, has heard the will read, or can identify a copy of the will.