1. Ensure at least one other program is running, with its window maximised.
2. Drag the pink square over the blue square. The mouse cursor should be the no-drop cursor, or the platform's drop-allowed cursor.
3. Without releasing the mouse button, use Alt+Tab (or your system's equivalent) to switch to the other program, then back to this one.
4. The mouse cursor should be the same cursor as in step 2.
5. Move the mouse outside the black square. The drag placeholder should follow the mouse (reappearing if it disappeared in step 2).
6. Release the drag. The drag placeholder should disappear, and the cursor should revert to the default mouse cursor.