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