JC is manufactured in the US, but afaik nobody does batch testing. My main concern is with the use of tainted ingredients, which you do need batch testing at least of the ingredients to protect against. I don't know that buying from a US PG or glycerine supplier is really going to be that much safer than buying from a Chinese one.
OTOH, there was a
thread elsewhere that compared one Chinese PG manufacturer to Dow, and on at least a few metrics, it could be said their "pharmaceutical grade" PG was equal to the Dow "industrial grade" PG. I don't know where the Chinese manufacturers source their PG, nor do I know where JC get theirs. Probably they don't really, either, since it will have passed through a number of hands before they get it.