I think it is not a matter of whether the test is rigged or
whether God knows the future. Surely God is not waiting to see the
result like us waiting for 4D results?
I think the tests are more for the protagonist than for God. God
might have known the result, but His intention was to let the
protagonist face the trial. A question to ponder - do you think
there are other protagonists who failed and their failure not
recorded in the bible? Maybe someone did sacrifice his son and the
angel lamented "I was too slow". 
You can say if you know the result, it wouldn't be fair. I say you
are looking from hindsight. It is like saying .. if I know
Singapore will succeed then the PAP have it easy. They will
eventually succeed right?
I say no .. it is because of the trials we faced and the choices
made by our leaders that we are what we are today.
My 2 cents (from my little understanding of Judaism). Judaism
teaches that it is only when you are able to choose between the
good and bad that goodness can be obtained.
