I hear you, but it's also a reality that more people in our field have heard "battle tested", know what it means and understand the French translation than "épr

I hear you, but it's also a reality that more people in our field have heard "battle tested", know what it means and understand the French translation than "épreuve du feu" (I genuinely only ever read that idiom, and not once since the horrible movie which got that as the French name). That's where I'm saying going back to an older idiom just makes it classic, and doesn't help communication in itself IMHO.