The testimony of Jesus is found in the Bible from Genesis to Revelation. He already told us that.
And beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself... And he said unto them, These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me. (Luke 24: 27, 44).
What is "Moses" and "the Law of Moses"? That is in fact the Torah (from Genesis to Deuteronomy -- 5 books). The we have "the Prophets" (8 books). Then we have "the Psalms" (11 books). For a total of 24 books in the Hebrew Tanakh ( equal to our 39 books of the OT). Then we have all 27 books of the NT. So this is "the testimony of Jesus". There is no need to be chasing after modern prophets (charlatans).