Testing Cat Converter with Non Contact Thermometer

I saw on-line that a catalytic converter can be tested for function using a non-contact thermometer (laser thermometer), by measuring temps at front and rear of the cat. Normal function is indicated by the rear being hotter than the front by a good margin. Is this a reliable way to test the cat? Also, I have 2 cats on the Liberty, so I can compare readings for both.

Also, would like to know what "normal" temps should be at the front and back of the cat. Thanks!

I would think an emissions test would be the best method to test for function.

The IR thermometer would be the best test to check for a clogged catalytic converter.