You will have to plug it into a Windows PC and test it with diagnostic software because all such software runs on Windows only - there is no Mac-compatible hard drive testing software that I'm aware of.
Unlike other drive manufacturer's, Toshiba don't actually have any diagnostic software for Toshiba branded drives but you can test it with Seagate's software called "SeaTools for Windows". Click "Downloads" on this page: http://www.seagate.com/support/downloads/seatools/
The software will tell you if the drive has failed. Use the "Long" or "Extended" test.
It doesn't matter that the drive is formatted for a Mac, the Windows diagnostic software tests the actual drive, not the data that's on it.