For a while, the strongSwan Debian package had an autopktest. The initial version was proposed by Christian Ehrhardt in 2016 (presumably especially for downstream use in Ubuntu) and updated in 2019, but since then not much at least in Debian.

With the metapackage dependencies update in 6.0.0-1 I had to tune a bit the tests dependencies so they wouldn't totally fail, and I noticed the amd64 tests were failing since basically the beginning (the other architectures would pass, but because the tests wouldn't actually run at all since they rely on the isolation-machine restriction which is not available there.

So I tried to fix them, and it actually took me quite a while because I wasn't able to run the tests locally easily and the salsa CI doesn't have the isolation-machine restriction either. And some tests would pass and not other.

With some nice help from #debci, and using my newly received X13G5 I set up an autopkgtest VM and started experimenting. The 6.0.0-4 autopkgtests were failing 19 times over 20 steps, but passing one time. So it looked like a race condition, which we narrowed to the fact that starting the daemons (using invoke-rc.d which calls systemctl) is asynchronous. So depending on the load and maybe the machine, the tests would usually fail but sometime pass.

There's no easy way to make the call synchronous, so as a stopgap I added a small sleep 1 command and it fixed it for now. Tada! strongSwan has now passing autopkgtests in unstable (and testing) amd64. It's not entirely satisfying but still.

Next steps would be to add tests for the new daemon using the swanctl inteface, but that'll be for Forky (Trixie+1).