Test car in the same day of the race

I have race tomorrow, and weather, so far,  will be overcast. As yesterday and today the weather is different from the day of the race, OF COURSE i'm going to test the car only tomorrow morning when the time is equal (i'm in my 1st season).

I think that to make things more interesting and chalenging, we shoudn´t be allowed to test the car in the day of the race, even if weather in other days is not the same.

That would bring more managers to not know what configuration to put on cars and probably we had more unpredictable races and results.
Of course managers who play this for "decades", maybe already know what to do as they been there on previous seasons...

Still, what do you think?

I think it'd be interesting, but if it's the same for everybody, nothing changes, and instead of a perfect setup everybody will drive with an equally setup that's slightly adrift of the ideal.

Also, I don't always have time. Sometimes I do testing on the same day, sometimes not, cause I don't have the time. 

Depending on which country the race is in you can still do a set-up an hour before the race in dry weather and then it rains during the race. So whether you do it the day before or an hour before makes little difference.  If it somewhere where the weather is generally stable then the same applies.

Or am I missing the point?