attest
adjure, affirm, assert, authenticate, aver, bear out, bear witness, certify, confirm, corroborate, declare, demonstrate, display, evince, exhibit, give evidence, invoke, manifest, prove, ratify, seal, show, substantiate, swear, testify, verify, vouch for, warrant, witness
Antonyms
contradict, controvert, deny, disprove, gainsay (archaic or literary) give the lie to, make a nonsense of, prove false, rebut, refute