Chris,
The airline I work for has a very intensive promotion structure, 1st a command assessment, then a command course, then supervised line flying with a training Capt. (although that doesn't always mean that 2 Capt's together means one is under training, just that as with our lot outstation Capt's do fly together.) so at any point during the process if the f/o doesn't pass they don't go on to the next.