testimony vs affidavit

testimony and affidavit both are nouns.

Word	Noun	Adjective	Verb	Adverb
testimony	Yes	No	No	No
affidavit	Yes	No	No	No

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

testimony: a solemn statement made under oath
affidavit: written declaration made under oath; a written statement sworn to be true before someone legally authorized to administer an oath

Other hyponyms of testimony include witness, declaration, attestation, subornation.

testimony (noun)	affidavit (noun)
a solemn statement made under oath	written declaration made under oath; a written statement sworn to be true before someone legally authorized to administer an oath
an assertion offering firsthand authentication of a fact
something that serves as evidence