The word(s) "testify" appears 18 time(s) in 15 verse(s) in Quran in Saheeh International translation.

(1) But when Jesus felt [persistence in] disbelief from them, he said, "Who are my supporters for [the cause of] Allah?" The disciples said, "We are supporters for Allah. We have believed in Allah and testify that we are Muslims [submitting to Him].

(2) Those who commit unlawful sexual intercourse of your women - bring against them four [witnesses] from among you. And if they testify, confine the guilty women to houses until death takes them or Allah ordains for them [another] way.

(3) Say, "What thing is greatest in testimony?" Say, "Allah is witness between me and you. And this Qur'an was revealed to me that I may warn you thereby and whomever it reaches. Do you [truly] testify that with Allah there are other deities?" Say, "I will not testify [with you]." Say, "Indeed, He is but one God, and indeed, I am free of what you associate [with Him]."

(4) Say, [O Muhammad], "Bring forward your witnesses who will testify that Allah has prohibited this." And if they testify, do not testify with them. And do not follow the desires of those who deny Our verses and those who do not believe in the Hereafter, while they equate [others] with their Lord.

(5) And do not approach the orphan's property except in a way that is best until he reaches maturity. And give full measure and weight in justice. We do not charge any soul except [with that within] its capacity. And when you testify, be just, even if [it concerns] a near relative. And the covenant of Allah fulfill. This has He instructed you that you may remember.

(6) And [mention] when your Lord took from the children of Adam - from their loins - their descendants and made them testify of themselves, [saying to them], "Am I not your Lord?" They said, "Yes, we have testified." [This] - lest you should say on the day of Resurrection, "Indeed, we were of this unaware."

(7) Return to your father and say, "O our father, indeed your son has stolen, and we did not testify except to what we knew. And we were not witnesses of the unseen,

(8) He said, "[No], rather, your Lord is the Lord of the heavens and the earth who created them, and I, to that, am of those who testify.

(9) They said, "Then bring him before the eyes of the people that they may testify."

(10) And [they are] those who do not testify to falsehood, and when they pass near ill speech, they pass by with dignity.