The Collaborative International Dictionary of English v.0.48:
Attest \At"test"\, v. t. [imp. & p. p. Attested; p. pr. & vb.
n. Attesting.] [L. attestari; ad + testari to bear witness:
cf. F. attester.]
1. To bear witness to; to certify; to affirm to be true or
genuine; as, to attest the truth of a writing, a copy of
Facts . . . attested by particular pagan authors.
2. To give proof of; to manifest; as, the ruins of Palmyra
attest its ancient magnificence.
3. To call to witness; to invoke. [Archaic]
The sacred streams which Heaven's imperial state
Attests in oaths, and fears to violate. --Dryden.