You would use existing case law to attempt to prove the existence or nonexistent of contractual intent. Some major cases that a person could draw supporting evidence are:
Lumbreras v Rocha
2012 Tex. App. LEXIS 97 (13th Dist. 2012)
All Star Championship Racing, Inc. v. O'reilly Automotive Stores, Inc.
2012 U.S. Dist. LEXIS 34951 (C.D. Ill. 2012)
