‘Combat testing’ is a made up term. Equipment/capability/materiel has already been extensively tested and accepted before it’s deployed to units. ‘Stuff’ isn’t tested in live environments (outside of extreme scenarios). This phase of the war is ‘verifying’ that the engineers it right. They’ll take notes and make improvements/tweaks for future upgrades or refurbishment of the capability.

You described whether a capability is ‘fit for use’; can the ‘thing’ do what it’s meant/designed to do when the user needs it. If said 18-24 year old doesn’t maintain their piece of equipment and it fails to function when required, that’s a failure on the NCOs or junior officers (NCOs being something the Russian army doesn’t have/develop), not because it isn’t ‘combat tested’.