I don't think you really need to test them at that age, or worry about enrichment... just follow their lead.
My DD(now 9) didn't say a word until 24 months but at 16 months knew the entire alphabet (you could ask for a letter and she'd point to it). This was because she was chasing me with books from 9-10 months on. I never "enriched" her - she enriched me, lol. Her comprehended vocab was insane. You ask her anything and she'd point to it.
I never enriched her. She came after me. Asking with her eyes - that intense, relentless stare. Books, objects, you name it - she'd point and look expectantly at me until I gave her a label for whatever she was pointing at. On and on and on. (I used to hide in the bathroom sometimes and say "go see Daddy for a minute!!") Not even kidding.
Anyway, just sit with your son, watch him, and let him ask you what he wants to learn. And have fun
