It’s my understanding that you don’t run it when the temp is under 65.
I have also been told that if the heat side works, then you can safely assume that the cold will also.
I could be wrong, about this, but I think it just runs in reverse to cool. So that being the case everything should be fine if heat mode works.
Also be sure to test the emergency heat mode as well. (That works more like an electric furnace.)