Every way this comes apart is silent. The string lives twice, once per frame, with nothing linking them. A misspelled key is not an error, it is upstream's default quietly coming back. lang.js moving below the loader stub costs the string everyone on a non-English browser. A missing font or insignia is a fallback face and a blank box. None of that is reachable without a browser, so this checks the pieces exist, say the same thing, and are wired in the right order.