As far as the views of the scholars of the Shafi’e Mad’hab are concerned, since the swab inserted through the mouth and nose for the COVID 19 Screening test does not go beyond the limits mentioned above (which has also been confirmed by the experts in this field), such a testing procedure will not invalidate the fast.
However, if it is proved with certainty that this instrument goes beyond the above mentioned limits, the fast will be nullified. The missed fast should be made up for on another day.