1 John 5:11

And this is the testimony: God has given us eternal life, and this life is in his Son.

(v11, NIV)

In this verse, we find out what the testimony is. We've known from what John has said already. We knew it was concerning his son. However, in this verse the testimony is focused in on eternal life. This life is in his Son, so the testimony is still about Jesus. However, the focus on this testimony about his son is on God who has given us eternal life. It is in Jesus Christ who we believe. It is Jesus who gave his life for us. But it was God who sent his son to die for us. God gives us eternal life through Jesus Christ his son and it only through him that we may live.