Is there any software that can test a Blu-ray that is in an external BD drive? I've heard of some in the past, but I'm not sure what it's called or even what the type of software would be called, so I haven't had any luck searching for it.
First, I don't have a real answer for you to work with OSX but I know in the past that people would do "bit perfect" ISO's within Windows and during the process, it could/would detect errors.
The one fly in the ointment is that not all player/readers are created equal. I have had some discs (CD, DVD and Blue Ray) that would not play in one unit but happily would be readable and play in another.
If you can do a bit perfect copy of a disc as an ISO it should be good to go. If it fails or stumbles you may have problems with the disc that the particular BD reader you are using is unable to read in those locations.