A.T. Robertson Commentary 1 Corinthians 1:6

"even as the testimony of Christ was confirmed in you:" — 1 Corinthians 1:6 (ASV)

Even as (καθως). In proportion as (1 Thessalonians 1:5) and so inasmuch as (Ephesians 1:4).

The testimony of Christ (το μαρτυριον του Χριστου). Objective genitive, the testimony to or concerning Christ, the witness of Paul's preaching.

Was confirmed in you (εβεβαιωθη εν υμιν). First aorist passive of βεβαιοω, old verb from βεβαιος and that from βαινω, to make to stand, to make stable. These special gifts of the Holy Spirit which they had so lavishly received (ch. 1 Corinthians 12) were for that very purpose.