Primary Test: There are s couple of methods used to identify a coating on a diamond. The most important is magnification and a tweezer. The coating being used on diamonds is extremely durable and cannot be scratched to the extent that it is easy to ID by simply running a tweezer point across the stone. The other issue is that the bottom of the diamond is the part coated, not the top (at least as of this writing). As a result the ID method should be performed on the pavilion of the stone and not the crown. The method is to run the tweezer point across the stone and then view the stone in overhead fluorescent light in a side reflected direction as shown below. What you will see is that the coating actually can be very slightly surfaced scratched, but that this only visible in overhead side reflected light. An example is shown below.
Secondary Tests: There is no secondary test that can be done by local retail jewelers. A scan using a Raman Microscope will provide a diagnostic readout, but this can be an expensive test if a major lab is used. The ISG can provide this service for a nominal fee for jewelers, gemologists, and appraisers.
Repair and Setting: This coating process has been found to be extremely durable. Do not heat the stone in a torch, but prong re-tipping has been reported with no problems as the coating is very durable as long as not in direct contact with flame.