prove-a-procedure-on-a-fixturelisted

# Prove a procedure on a fixture Documentation that ships commands is untested code with a readership. Nothing compiles it, no suite runs it, and its failures are silent in the worst direction: a step that errors is discovered immediately, while a step that answers *confidently and wrongly* is followed. Reading it is not verification. The reader is not going to read it; they are going to run it. A fixture is cheap, and it is the only thing that separates a procedure that works from one that reads as though it does. ## Procedure 1. **List the cases the text claims to handle, in its own words.** Quote the claim. "Classifies every dirty path" is a list: modified, deleted, renamed, untracked, already-landed. A claim you cannot turn into cases is too vague to verify, and that is itself the finding. 2. **Add the awkward cases the prose implies but never names.** These are where confident wrongness lives, and each one is a real defect found this way: | Shape | What it breaks | |---|---| | a path containing a space | quoting, and any `read` that splits on it | | a path beginning with `-` | every command that parses it as an option | | a symlink | tools that follow it and compare the wrong thing | | a binary file | line-based logic that reports zero differences | | a mode-only change | byte comparisons that call it unchanged | | an empty result | loops that treat "nothing" as "done" | 3. **Build one throwaway fixture holding all of them**, ou