Gaiu Trebatius Testa, an equestrian (see equites) Roman lawyer to whom *Cicero, a close friend, dedicated his Topica (‘Topics’). Cicero having recommended him to *Caesar as legal adviser, he enjoyed the latter's favour and later that of *Augustus (see also Hor.Serm. 2. 1. 4 f.). An ingenious casuist whose extensive writings do not survive, he persuaded Augustus that informal codicils could properly be recognized as valid (Justinian, Inst.