This test is only relevant on platforms where it is possible to switch applications in mid-drag (eg. alt+tab, dragging over taskbar buttons, dragging between restored windows).
This testcase requires an external application that accepts dragging and dropping of files - eg. your system's file manager. Ensure that two application windows are open for the external application, showing different folders.
Select a file in the first external application window. Drag the file over the browser window, then over the other external application window and release it. Pass if the file is copied/moved to the second window, as expected by the system.