Since ChefSpec 7.1.2, the coverage reporting within ChefSpec is deprecated.
If you have coverage reporting enabled, you will see the follwoing warning in your ChefSpec logs:
ChefSpec's coverage reporting is deprecated and will be removed in a future version
Unfortunately the team don't want to support this as they recommend focussing test efforts on the logic-heavy portions of the cookbook rather than testing everything.
Note that you will not see this message until you have ChefDK 2.5.3 or higher.