“Might find out if the S-400 SAM works as advertised.”
I think Israel has been beating it semi-regularly.
Never forget that half the ‘fun’ of war for the brass and politicians is seeing if their multi-million dollar ‘toys’ work, as described by the manufacturer. Usually this is accomplished through proxies. Today, there are few proxies to test these systems.
With so many pols having been bought off. and/or having given the Chicoms so many secrets, the Rooskies likely have bought/been provided with, most Western secrets.