1 John 5:6-12 (NASB)

6    This is the One who came by water and blood, Jesus Christ; not with the water only, but with the water and with the blood. It is the Spirit who testifies, because the Spirit is the truth.

7    For there are three that testify:

8    the Spirit and the water and the blood; and the three are in agreement.

9    If we receive the testimony of men, the testimony of God is greater; for the testimony of God is this, that He has testified concerning His Son.

10  The one who believes in the Son of God has the testimony in himself; the one who does not believe God has made Him a liar, because he has not believed in the testimony that God has given concerning His Son.

11  And the testimony is this, that God has given us eternal life, and this life is in His Son.

12  He who has the Son has the life; he who does not have the Son of God does not have the life.

There are Four Indisputable Testimonies:

1. The Apostle John
2. The Holy Spirit
3. God the Father
4. The believer

Additionally, there are testimonies about Jesus in John 5:31-46:

John the Baptist, the works of Jesus, God the Father, the Scriptures, and Moses.