Allen's test used for detecting integrity of palmar arch tests which of the following?

Allen's test allows assessment of the extent of connection between the radial and ulnar aeries through the palmar arches. In Allen's test: the examiner compresses both the radial and ulnar aeries at the wrist and then asks the patient to flex and extend the fingers repetitively. After the hand blanches, pressure from the radial aery is released while compression is maintained on the ulnar aery and the examiner observes how long it takes for each of the fingers to regain its pink color. The initial step is repeated with both vessels compressed, and the ulnar aery occlusion is then released while pressure is maintained on the radial aery. Again, examination of the reperfusion of the fingers reveals which digits are primarily supplied through the ulnar aery. Ref: CURRENT Diagnosis & Treatment in Ohopedics, 4e chapter 10