to bear witness to; certify; declare to be correct, true, or genuine; declare the truth of, in words or writing, esp. affirm in an official capacity

to attest the truth of a statement.

to give proof or evidence of; manifest

His works attest his industry.

to put on oath.

to testify or bear witness (often fol. by to )

to attest to the reliability of an employee.

Archaic . witness; testimony; attestation.

noun

attester , testifier