Just because God knows the choices people make beforehand doesn't mean it's a test. Like Adam and Eve God didn't test them by forcing them to hide among the trees. God speaks within human comprehension, so it may seem like He is asking a question and He is except He knows the answer like a teacher teaching a class.
I would add into the mix that God himself states that he is a jealous God.
Is it really so unreasonable to suggest that If Abraham's love/focus on God was lessoned by his Son that God would not want to test this?
Afteralk, Who tolerates uncertainty?