I've read the FAQ on this and the reasoning listed is that you have to have OC Scanner installed for the Test button to be enabled on Precision.
I've tried installing Precision first, then OC Scanner and vice versa. I've tried opening one before the other. I've checked the box to link OC Scanner to Precision.
Nothing seems to connect the two. I must be doing something obviously wrong, right? It's only a minor annoyance, but it wasn't an issue for me when I had the old versions of the software and my GTX 570 (upgraded to GTX 970 and the latest software yesterday).