apple hardware test fails to finish

MacBook Pro has frozen me out. Can't even extract files using my iMac & target disk mode. If I wait a long time, eventually I get a User folder icon, but when I enter it & click on the Documents folder icon nothing appears. If I click on the documents icon & click "get info" it reads a folder of over 17GB, but I can't see or extract them. So, thought I'd run an internet hardware test (as it's about the only thing I haven't done!) to see if that could shed any light on the matter. Short test failed to finish 3 times after 1.37 minutes with about 3mm left to go on the progress bar. I waited about 30 mins each time before trying again. Initiated the long test & left the house. Returned 6 hours later to find it stalled after 15 mins 19 seconds with the same amount of distance to go on the progress bar.

The OS has been failing bit by bit over the period of about a week. Couldn't get in with a regular boot so went in with safe mode & took off important files. After a few visits in safe mode I was frozen out of that also. Recovery mode still boots so I'll reinstall the OS I guess. Just wondered if anyone could shed any light on the problem.

MacBook Pro9.1 - Quad Core i7 - 230GHz - 4GB RAM - osx 10.8.5