generated at
testify

verb (testifies, testifying, testified) no object
〈人が〉 «…に不利に/…について/…に有利に/…に対し» (法廷で宣誓の上)証言する «against/about/for/to» ; 〈人が〉 «…(の真実性)を» 証明, 立証, 保証する «to»
e.g. he testified against his own commander
e.g. with clause : he testified that he had supplied Barry with crack.
serve as evidence or proof of something's existing or being the case:
⦅かたい書⦆ 〈物・事が〉 «…の» 証拠となる «to»
e.g. the bleak lines testify to inner torment.

DERIVATIVES
testifier | ˈtestəˌfī(ə)r | noun

ORIGIN
late Middle English: from Latin testificari, from testis ‘a witness’.