Ok well what I do is eat dinner a bit earlier on the day I'm doing the test, about 5-6pm and do insulin as usual but do not eat again! And just drink water, nothing with any carb in it. Then 4 hours after you've eaten the test "starts". For me that's 11pm. Take a BG reading then head off to sleep. Alarm set for about 12.30am, take BG and back to sleep. 2am test again and so on until morning. If at any point you go hypo, correct it then stop the test by he next day reduce insulin by 1unit and do the test again.
You should see a pattern of what your body does over night. In theory, if your basal is correct then your BF should stay steady. Mine does, but that's mostly down to the honeymoon period! So my body is cheating a little bit
you may find you're going hypo at some point, if that's the case then your body is correcting itself and resulting in a morning high.
If you stay steady all night but then suddenly rise in the early hours of the morning then it's the dawn phenomenon most likely. I think the general rule is do it for 3 nights, if its the same all 3 nights then it's considered a pattern
I hope that makes sense