Definition of "Attest" :

verb: authenticate, affirm to be true, genuine, or correct, as in an official capacity

"I attest this signature."

verb: establish or verify the usage of

"This word is not attested until 1993."

verb: provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes

"His high fever attested to his illness."

verb: give testimony in a court of law