Testing procedure:

1) Testing proper 'lvs' output:
'lvs' has two new reportable fields (not printed by default): "syncaction" and "mismatches".  It must be possible to report these fields and have them be correct.  (This can be done while testing scrubbing functionality - i.e. #2 below)

Ex1> lvs -o syncaction --noheadings vg/lv
  Answer depends on current operation and can be:
     - idle:   All sync operations complete (doing nothing)
     - resync: Initializing an array or recovering after a machine failure
     - recover: Replacing a device in the array
     - check: Looking for array inconsistencies
     - repair: Looking for and repairing inconsistencies
An attempt should be made to validate these states are printed correctly.  During an initial sync, it should read 'resync'.  When finished, it should read 'idle'.  When replacing a device in the array, it should be 'recover'.  etc.

Ex2> lvs -o mismatches,attr --noheadings vg/lv
  Should be '0' at all times unless a "check" has been performed and discrepancies have been found in the array.  The last character in the attribute field should also read 'm' if there are mismatches after a "check" has been run.  (Note that in the case of a device failure or device transient failure, the 'p'artial and 'r'place/'r'efresh flags take precidence over the 'm'ismatches flag.)

2) Testing correctness of scrubbing operations:
There are currently 2 scrubbing operations which can be performed: "check" and "repair".  To test them, do the following (or similar):

for all RAID types {
  for all devices in the array {

    Create RAID array
    Wait for sync
      - 'lvs -o syncaction' should be "resync"
      - 'lvs -o sync_percent' should grow to 100%
    Perform "check" (lvchange --syncaction check vg/lv)
    Wait for sync
      - 'lvs -o syncaction' should be "check"
      - 'lvs -o sync_percent' should grow to 100%
    'lvs -o mismatches' should be 0

    Deactivate RAID array
    Write crap to $device (inner for loop)
      - if writing to PV directly, be sure to skip over LVM label, etc
      - lvm2/test/shell/lvchange-raid.sh has example of how to do this
    Activate RAID array

    Perform "check" (lvchange --syncaction check vg/lv)
    Wait for sync
      - 'lvs -o syncaction' should be "check"
      - 'lvs -o sync_percent' should grow to 100%
    'lvs -o mismatches' should be NON-ZERO

    Perform "repair" (lvchange --syncaction repair vg/lv)
    Wait for sync
      - 'lvs -o syncaction' should be "repair"
      - 'lvs -o sync_percent' should grow to 100%
    'lvs -o mismatches' should be 0

    Perform "check" (lvchange --syncaction check vg/lv)
    Wait for sync
      - 'lvs -o syncaction' should be "check"
      - 'lvs -o sync_percent' should grow to 100%
    'lvs -o mismatches' should be 0
  done
done

3) Other sanity checks:
  - You must not be able to start a "check"/"repair" while another sync operation is happening.
  - If throttling is available, it should function on "check" and "repair".  (https://bugzilla.redhat.com/show_bug.cgi?id=969171#c3 is the RHEL6 test suggestions for throttling.)

In addition to the commit in comment 0, there is a fix for a segfault that must also go in:

commit 4eea66019157abd992c8802564b675fd97420c01
Author: Jonathan Brassow <jbrassow>
Date:   Fri Jul 19 10:01:48 2013 -0500

    RAID: Fix segfault when reporting raid_syncaction field on older kernel
    
    The status printed for dm-raid targets on older kernels does not include
    the syncaction field.  This is handled by dev_manager_raid_status() just
    fine by populating the raid status structure with NULL for that field.
    However, lv_raid_sync_action() does not properly handle that field being
    NULL.  So, check for it and return 0 if it is NULL.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2013-1704.html