FYI. I came across this libkqueue test failure in a PR test today.
https://ci.swift.org/job/swift-corelibs-foundation-PR-Linux/389/console
FAIL: kqtest
···
============
bind-1: Address already in use
Running 1 iterations
1: test_peer_close_detection() 2: test_kqueue() 3: test_kevent() 4: test_ev_receipt() unable to bind to port 23456
*** TEST FAILED ***
Pushkar N Kulkarni,
IBM Runtimes
Simplicity is prerequisite for reliability - Edsger W. Dijkstra