Hey,

I have a group of GenServers which form a “unit” together with its parent Supervisor. One GenServer holds the state, another one sends data to external services and a third one is responsible for terminating the whole unit after a certain amount of inactivity.

Currently, if there is no input for 30 minutes, the “Timeout” GenServer terminates the parent Supervisor and therefore the whole unit. However, if the unit is in pause mode, the 30-minute timeout gets ignored and a 24-hour timeout gets started which is just a fallback to eventually clean up the system.

Right now, that whole thing is “untested”, which simply means it has no automated tests. It works fine but it’s also not that complicated at the moment. It might get a bit more features in the future tho.

I would like to write some simple integration tests but I am unsure how to deal with the timing aspect.

One thing to note is that I can manually override the timers in the Timeout GenServer. That was needed to reinitiate them after a reboot (e.g. deployment). I am sure that comes to my advantage in regards to testing but I still have no idea how to best structure the test.

The quick and dirty way would be this:

1. Start “unit”
2. Send input to “unit”
3. Manually override timeouts
4. Process.sleep() in Test module
5. Assert expected state

But using Process.sleep() in the test Module (even if it’s for 1 second) feels quite dirty.

Any other suggestions?