If you look at the change below, you'll see that permission_types was never used and now it is.  I added the default value because that was what it was using in line 40 so it seemed fair to make it the default value.  It made the test a little simpler as access_controls_enforcement#discovery_permissions is protected and can't be accessed so I would have had to hard-code the same list (discover, read, edit) in the test which felt wrong.