The Abraham and Isaac story is (I believe, & aside from being a test) a teaching moment for both Abraham and Isaac. Through demonstration, God gave both Abraham and and Issac a visceral understanding of what it meant to Himself and His son, Jesus Christ to provide the atonement for mankind. God the Father sacrificed His Son and our Savior, Jesus Christ, for the sins of the world.
At one point in the story, Isaac asks Abraham: "... but where is the lamb for a burnt offering?" I happen to believe that at that moment of inquiry, Isaac understood that he was to be the sacrifice... and... that he went voluntarily. There is no mention of a struggle in the text where Isaac resisted being sacrificed. Likewise, Jesus Christ volunteered to be a sacrifice for our sins to appease the demands of justice for our sake on condition of repentance.
The whole episode gives us an emotional conception of what it meant to our Heavenly Father to sacrifice His only begotten son in the flesh to us, on a personal level. But whereas Isaac was not sacrificed, Jesus Christ actually suffered the pains and torture of death and hell on our behalf and He did it out of love for us.