informant vs attester

informant and attester both are nouns.

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

As nouns, attester is a hyponym of informant; that is, attester is a word with a more specific, narrower meaning than informant:

informant: someone who sees an event and reports what happened
attester: someone who affirms or vouches for the correctness or truth or genuineness of something

Other hyponyms of informant include attestant, deponent, deposer, testifier.

informant (noun)	attester (noun)
a person who supplies information	someone who affirms or vouches for the correctness or truth or genuineness of something
someone who sees an event and reports what happened