The verb attest has 4 senses (first 2 from tagged texts)
1. (2) attest, certify, manifest, demonstrate, evidence -- (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")
2. (1) attest -- (authenticate, affirm to be true, genuine, or correct, as in an official capacity; "I attest this signature")
3. testify, attest, take the stand, bear witness -- (give testimony in a court of law)
4. attest -- (establish or verify the usage of; "This word is not attested until 1993")