Hmmm... That's an interesting and thoughtful point if view as far as theology goes. Do your beliefs stem from a specific religion, or are they more solitary beliefs of yours?
I follow a specific religion. The Church of Jesus Christ of Latter-day Saints.
Also, life as a test is hardly fair... What lesson is there for a spirit to learn as a toddler who's life is cut short because of a brain tumor, or as a severely autistic individual who is forced to be trapped within the universe they construct within their own mind for their entire life?
Mortal life can definitely be unfair - however - I believe that truth has been revealed that offers some solace.
Joseph Smith - the man I believe was a prophet of the Lord Jesus Christ - had many children with his wife - but most of them died either in infancy or when they were extremely young.
He claimed that he often pondered on these types of questions. Why do they live only to be snuffed out so soon? Why are so many people born with infirmities of mind and body if the point is for them to excel in this life?
He also claimed that he received some revelation on these topics and was comforted by them.
First - one of the main reasons that we enter into mortality - other than to be tested - was to obtain our own physical body.
Up until that point in our existence - we were spirits - only composed of spirit matter. We did comprehend pleasure and pain, sweet and bitter, energized or tired, health or sickness - good and evil.
There needs to be a time set aside for us to experience these things. And there is a promise that all of us will be able to keep our physical bodies at the conclusion of this world - much like the Lord Jesus Christ.
Second - he claimed that all of us knew the conditions that would be placed upon us before we entered this life - and we all agreed to them.
The toddler that died from a brain tumor knew what would happen - and felt that it was worth it - because even though their mortal life was brief - it allowed them to inherit a physical body that they will be reunited with it for an eternal inheritance at the moment of their Resurrection.
Third - their being born into mortality ensured that they entered into a family - and because of the promises made to Adam and Eve - they would be redeemed as a family unit and know joy from that relationship.
Fourth - there are certain ordinances that can only be performed in mortality. Things that need to take place while time is in effect. Everyone who has entered into mortality - even if they leave it early on - will have the opportunity to have these ordinances performed on their behalf.
Fifth - any and all infirmities placed upon us in mortality are temporary - and only have place in mortality. Mortal life is only a *blip* in our eternal existence. An important *blip* - but still a *blip* - and once we are Resurrected - all our infirmities of mind and body will be gone.
Sixth - our Father knew us intimately before we came to this world and therefore many of the infirmities that are placed on us are given to us to help us along our journey. To teach us something or push us in the right direction. We need to learn from them.
This is not to say that everything that happens to us is planned out completely - because imperfect mortality will always bring in some randomness.
Lastly - those who died before reaching the age of accountability - the age where they can appropriately discern good from evil - or those who live without being accountable - will be considered completely innocent at the time of their death - therefore they will immediately be ushered back into the arms of the Father. No need for Judgment.
Many of those who die before the age of accountability or who live without accountability (like with extreme cases of autism) are those spirits who did not need the rigors of mortal life to excel. They have already attained a level of excellence - and there was no need to test them further - and all they needed from mortality to grow was to obtain a physical body, inherit the promises made to Adam, enter into a family unit and receive gospel ordinances.
So they agreed to enter into mortal life - not only for their own benefit - but to be a benefit to others. They were here to help someone else learn something. To help them see a portion of the truth.
I know this last one to be true because I lost a son when he was a baby and I have two sons who are autistic - one severe - and I know that even though these things can be painful - I'm grateful for them.
Wow. I'm literally crying right now. Good time to end.