A somewhat difficult method, but one suggested by Intel in this forum in the past, is installing it in another (X58) mother board PC that is known to work, and see what the result is.
Otherwise, I am not aware of a standard or simple (or difficult) test procedure for testing CPUs, such as with a volt meter or other equipment. How does Intel do that? Who knows...
So the CPU looks fine on the bottom? No burn marks on the pads? The CPU socket is obviously Ok according to Gigabyte.