attest vs attester

attest is not a noun while attester is a noun.

Word	Noun	Adjective	Verb	Adverb
attest	No	No	Yes	No
attester	Yes	No	No	No

attest (noun)	attester (noun)
	someone who affirms or vouches for the correctness or truth or genuineness of something

attest (verb)	attester (verb)
authenticate, affirm to be true, genuine, or correct, as in an official capacity
provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes
give testimony in a court of law
establish or verify the usage of