Definitions of attest:

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

  Example: "I attest this signature"

• verb:   establish or verify the usage of

  Example: "This word is not attested until 1993"

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

  Example: "His high fever attested to his illness"

• verb:   give testimony in a court of law