Unfortunately, or perhaps, fortunately, because human bodies are not exactly replicable, everyone has a slightly different experience.
A small rise or fall, of maybe 2mmol, over a time period is probably ok, but obviously that is dependent on the starting point. If you start on 4mmol and it drops 2mmol, that is not good at all. Whereas if you go to sleep on 7.5mmol, and wake on 5.5mmol then that is just fine.
There are so many caveats here, it's hard to give advice, it has to be a matter of judgement. I suppose the question is does your basal dose keep you within your target range, overnight, and during the day, when there isn't any other insulin on board, The night time is easier to test than the day time,as we don't eat then.
But you can do a basal test on the daytime.