God not only has faith, he has knowledge that we would not leave him. Thats why he gave job over to satan. God knew what the outcome would be.
God does not act on faith in the unknown. He acts on the known
I meant to emphasize that God loves us and trust in our goodness which He Himself placed it there. Instead of thinking of God as a blind force who decides to take away all your family, all your fortunes, to give you disease just to see what happens, just to make an experiment on you, I believe God trusted His creation.
So, I believe the test is in an paradoxical way for both God and Job.
Satan wants to show God that His creatures are loving Him only under certain conditions. And Satan also wants to show Job that God is unjust towards Him and doesn't care about his loyalty and love. At the end, Satan is defeated by the love that exists between God and His creature.