testimony vs testament

testimony and testament both are nouns.

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

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

Other hyponyms of testimony include good authority.

testimony (noun)	testament (noun)
a solemn statement made under oath	a profession of belief
an assertion offering firsthand authentication of a fact	a legal document declaring a person's wishes regarding the disposal of their property when they die
something that serves as evidence	strong evidence for something