Comment by Jtsummers

For the example it would be easily caught with PBT by testing the left and right identities for addition.

In general though, the advice is don't excessively dogmatic. If you can't devise a property to test, use traditional testing with examples. It's not that hard. Same way to deal with the problem of end-to-end tests or unit tests not being useful for certain things, use the appropriate test style and approach to your problem.