even as the testimony to Christ was confirmed among you—
καθὼς τὸ μαρτύριον τοῦ Χριστοῦ ἐβεβαιώθη ἐν ὑμῖν,
Even as the testimony of Christ was confirmed in you. Under the color of praises and thanksgiving he touches them sharply. For not by heathen philosophy, says he, neither by heathen discipline, but the grace of God, and by the riches, and the knowledge, and the word given by Him, were you enabled to learn the doctrines of the truth, and to be confirmed unto the testimony of the Lord; that is, unto the Gospel. For you had the benefit of many signs, many wonders, unspeakable grace, to make you receive the Gospel. If therefore you were established by signs and grace, why do you waver? Now these are the words of one both reproving, and at the same time prepossessing them in his favor.
Haydock Catholic Bible Commentary: 1 Corinthians
As the testimony of Christ, what Christ testified and taught was confirmed in you, that is, your faith in Christ hath been confirmed by those graces and gifts which you received from the Holy Ghost at your baptism, and when by imposition of hands you were confirmed by me, or some other bishop. Wi.