This attribute is the type of the test to be run. The diskRead test
reads every sector on the disk once and reports bad sectors. The
filesystemCheck does a sanity check and attempts to repair
corruption. The flakyBitDetection test reads every sector on the disk
twice and compares the two read results. The surfaceAnalysis test
writes a magnetically hard to record pattern to the disk and reads
back the pattern to determine the condition of the magnetic surface
of the disk. The surface analysis test destroys all the data and disk
should be formatted afterward.