The command refused every real invocation. Go's flag package stops
parsing at the first non-flag argument, so with the positionals first —
the order that reads correctly — `--from -` stayed among them and the
count check rejected it.
The host's own parser carries a note about this exact fault, and the
version it describes is worse: there a flag somebody passed was silently
ignored and the command succeeded anyway. This one at least refused.
The tests did not catch it because every case in them was a rejection.
The command was broken in the only way that matters — it refused what it
is for — and the suite was green. The lab found it at the first call.
Two tests now: the helper, and the command itself with a --from naming a
file that is not there, so the complaint must be about the file rather
than about usage. The second exists because injecting against the first
stayed silent: testing the helper alone left the command free to ignore
it entirely.