attest

provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes; "His high fever attested to his illness"; "The buildings in Rome manifest a high level of architectural sophistication"; "This decision demonstrates his sense of fairness"

authenticate, affirm to be true, genuine, or correct, as in an official capacity; "I attest this signature"

give testimony in a court of law

establish or verify the usage of; "This word is not attested until 1993"