How likely is your son to cooperate with testing? I think the answer is so idiosyncratic to the child's temperament.
For my DS-almost-3, I have zero doubt that he would answer in jokes and disguise his knowledge, so it would be a wasted effort for us to test at this age.
OT, but I will raise my hand for the roll call of mothers who expected to return to work when their child became school aged, but who are now planning a sojourn into homeschooling. It's a relief to think of homeschooling our equivalent of pre-K next year and following a wait-and-see approach for kindergarten. If he starts to do algebra in kindergarten, we'll know we made the right call. (I'm only half-joking there.)
