Magic is testable.
God exists outside the universe, magic within.
That a god exists outside of the universe - are we talking about a multi universe interpretation? My understanding is that many of the gods humans have invented are really thought to be within the universe, at least temporarily. Tor, Oden certainly are. And in other beliefs they are part of nature itself.
The biggest group of people that believe in any God believe in an Abrahamic. The next biggest group are pantheists which is a different concept of God but still distinct from magic.