Running in a loop, about 10 times minimum, will create this flay behaviour:
```
# echo "parallelism=8" >> /etc/kyua/kyua.conf
# cd /usr/tests/
# kyua test sys/kern/unix_passfd_test && echo yes
sys/kern/unix_passfd_test:empty_rights_message -> passed [0.002s]
sys/kern/unix_passfd_test:send_and_cancel -> passed [0.002s]
sys/kern/unix_passfd_test:send_and_close -> passed [0.002s]
sys/kern/unix_passfd_test:send_and_shutdown -> failed: /usr/src/tests/sys/kern/unix_passfd_test.c:368: openfiles() == nfiles - 1 not met
[0.002s]
sys/kern/unix_passfd_test:simple_send_fd -> passed [0.002s]
sys/kern/unix_passfd_test:simple_send_fd_msg_cmsg_cloexec -> passed [0.001s]
sys/kern/unix_passfd_test:truncated_rights -> passed [0.001s]
sys/kern/unix_passfd_test:rights_creds_payload -> passed [0.006s]
sys/kern/unix_passfd_test:two_files -> passed [0.001s]
sys/kern/unix_passfd_test:devfs_orphan -> passed [0.008s]
sys/kern/unix_passfd_test:copyout_rights_error -> passed [0.009s]
sys/kern/unix_passfd_test:bundle_cancel -> passed [0.010s]
sys/kern/unix_passfd_test:bundle -> passed [0.010s]
Results file id is usr_tests.20220519-190658-169250
Results saved to /root/.kyua/store/results.usr_tests.20220519-190658-169250.db
12/13 passed (1 failed)
```