1 to give evidence, especially in a law court: “He agreed to testify in behalf of / against the accused man.”
getuigen

2 to show or give evidence of; to state that (something) is so: “I will testify to her kindness.”
getuigen van
© K Dictionaries Ltd.

Vraag professionele hulp bij het schrijven van zakelijke, academische of persoonlijke teksten in het Engels door native speakers.

to testify	getuigen (ww.)
testify	certificeren

Bron: Wakefield genealogy pages