approval vs testimonial

approval and testimonial both are nouns.

Word	Noun	Adjective	Verb	Adverb
approval	Yes	No	No	No
testimonial	Yes	Yes	No	No

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

approval (noun)	testimonial (noun)
the formal act of approving	something that recommends (or expresses commendation of) a person or thing as worthy or desirable
a message expressing a favorable opinion	something given or done as an expression of esteem
a feeling of liking something or someone good	something that serves as evidence
acceptance as satisfactory

approval (adjective)	testimonial (adjective)
	of or relating to or constituting testimony
	expressing admiration or appreciation