The Gospel and the Letters of John contain a lot of language of an adversarial, litigation-type, language. "Testimony" and "judgment" are words that appear often. Jesus' "testimony" about himself and his mission were manifested in his words and actions. That would include not only his miracles, as seen in today's gospel from the Gospel According to Luke, but his teachings as well. The Sermon on the Mount in the Gospel According to Matthew stands out as a kind of "catechism" of Christian life. Jesus, himself, told the disciples that even if they didn't believe his words, his "works" should be adequate testimony. [John 10:37-38]. Jesus' ultimate testimony of his identity would be his death and resurrection.
In the USA (and elsewhere), a person giving "testimony" in a legal proceeding is required to "tell the truth, the whole truth, and nothing but the truth, so help me God." (Those last four words may be omitted in some places!) If we profess to be true disciples of Jesus, do our lives tell "the truth, the whole truth, and nothing but the truth" about our faith? If we were arrested for being a Christian, would there be enough evidence to convict us in either our words or actions? AMEN