Your title suggests 2 different testimonies, as does "hyper grace" doctrine, which I showed already.
The Father says, i paraphrase, "he who does not believe in the son does not believe in me.; Here is my beloved son; listen to him;"
The Son says, i have revealed my Father to you. i have revealed that Him and i are one, so go ye into the world and testify of me! many in the world claim to know God without the testimony of the Son.
when you testify of the Son you are equally testifying of the Father bc you can't testify of the son without mentioning the Father .
Therefore the church's duty(assignment) is to testify of the Son whom the Father has sent; bc the testimony of the Son is based on that of the Father.
Brief, the Son revealed the Father to the church and sends the church to reveal Him(the Son) to the world!
you are so eager to condemn grace preachers so much that you cannot see the link between the two testimonies!