LEDA 6.3 has known I/O bugs, that were reported, and are fixed in LEDA 6.4. We have to deactivate that test, because it loops forever with LEDA 6.3.
Current version of leda-numbers still fails. :-(
When LEDA is available, that test program tests very basic I/O operations of `leda::rational`. That also tests the link with LEDA.