MDL-33587 Add unit tests for stored_file::delete_reference()
MDL-33587 Add unit tests for stored_file::delete_reference()

The first unit test forces the File API to be more picky as any sane
core API should be. The second one illustrates the buggy behaviour of
the current implementation of delete_reference(). They both fail at the
moment, of course...

dilawar/moodle