For whatever reason, NuSMV2.7 generates multiple xml files, prefixed with some index, for the command file FRET produces when doing test case generation. It tries to prefix the filename you give it, which in this case is the absolute path in the system, leading to it trying to make a 1_/home/user/Documents/... which obviously fails.
For whatever reason, NuSMV2.7 generates multiple xml files, prefixed with some index, for the command file FRET produces when doing test case generation. It tries to prefix the filename you give it, which in this case is the absolute path in the system, leading to it trying to make a 1_/home/user/Documents/... which obviously fails.