how to test if a work item approval has been deleted during a work item save operation?

Hello,
  I've written a simple operation advisor (precondition) which is executed in response to a work item save operation.
  The advisor has to verify if a work item approval has been removed prior to saving the work item.
  For that purpose the advisor gets the old and the new state (of type IWorkItem) of the work item, fetches their approvals and the corresponding approval descriptors, and verifies if all approval descriptors of the old state are present in the new state. If one of the old state approvals is missing in the new state (verified by the descriptors' equals method) the advisor concludes that an approval has been deleted.
 Another test case is: Instead of deleting the existing approval, the tester creates a new one (along with the existing approval).

  In order to make a test I created a story work item with an approval of type "review".
  Then another approval is created and the work item "Save" button is clicked.
  As a result:

  - the list with approvals fetched from the old and the new states of the work item are different objects.
  - the list with approval descriptors, which are fetched from the old and the new states of the work item are different objects.
   - The corresponding IAapproval and IApprovalDescriptor objects are also different (although only a new approval is created and the existing one is not changed. I'd expect that at least the descriptor of the first approval is the same object in both states).
   - There is no unique approval descriptor ID which can be used to compare old and new state approvals.

Is there a way to test if an approval has been deleted prior to saving the work item?

Your help would be really appreciated!

Source code
Environment: RTC 5.0.2

    public void run (AdvisableOperation operation,
                              IProcessConfigurationElement advisorConfig,
                              IAdvisorInfoCollector collector,
                              IProgressMonitor monitor)
            throws TeamRepositoryException {
        workItemServer = getService (IWorkItemServer.class);

        Object data = operation.getOperationData();
        ISaveParameter saveParameter = null;
        if (data instanceof ISaveParameter) {
            saveParameter = (ISaveParameter) data;

            IAuditable oldState = saveParameter.getOldState();
            // test for newly created work item
            if ( (oldState == null)
                 || !(oldState instanceof IWorkItem)) {
                return;
            }

            IWorkItem oldStateFull = (IWorkItem)
                      workItemServer
                      .getAuditableCommon()
                      .resolveAuditable ((IWorkItem) oldState,
                                                    IWorkItem.FULL_PROFILE, null);
            IApprovals oldApprovals = oldStateFull.getApprovals();

            IAuditable newState = saveParameter.getNewState();
            if ( (newState == null)
                 || !(newState instanceof IWorkItem)) {
                return;
            }
            IWorkItem newStateFull = (IWorkItem)
                      workItemServer
                      .getAuditableCommon()
                      .resolveAuditable ((IWorkItem) newState,
                                                    IWorkItem.FULL_PROFILE,
                                                    null);
            IApprovals newApprovals = newStateFull.getApprovals();

            List<IApprovalDescriptor> oldDescrList =
                                                       oldApprovals.getDescriptors();
            List<IApprovalDescriptor> newDescrList =
                                                      newApprovals.getDescriptors();

            if ( oldDescrList.size() > 0 ) {
                final Iterator<IApprovalDescriptor> itOldList =
                                                         oldDescrList.iterator();
                while ( itOldList.hasNext() ) {
                    IApprovalDescriptor oldDescr = itOldList.next();
                    System.out.println("Print old descriptor to compare");
                    printDescriptorInfo( oldDescr, null );
                    final Iterator<IApprovalDescriptor> itNewList =
                                                                   newDescrList.iterator();
                    boolean found =false;
                    while (itNewList.hasNext()) {
                        IApprovalDescriptor newDescr =
                                                           itNewList.next();
                        System.out.println("Print new descriptor to compare");
                        printDescriptorInfo ( newDescr, null);
                        if (oldDescr.equals(newDescr) ||
                           (oldDescr == newDescr) ) {
                            found = true;
                            break;
                        }//if
                    }//while

                    if( !found ) {
                        String[] values = { String.valueOf (oldStateFull.getId()),
                                            oldDescr.getName(),
                                            oldDescr.getTypeIdentifier() };
                        String description = NLS.bind (
                                "Work item with id ''{0}'' cannot be saved as the approval with name ''{1}'' of type ''{2}'' has been deleted.",
                                values);
                            
                        IAdvisorInfo error =
                                 collector
                                .createProblemInfo ("Unable to save the work item",
                                                                description,
                                                                "Error");
                        collector.addInfo (error);
                        break;
                    } else {
                        System.out.println ("Approval "
                                                       + oldDescr.getName()
                                                       + "is found in the new work item state");
                    }//else
                }//while
            } else {
               System.out.println (
                          "No approval descriptors in old state");
            }
        }//if saveParameter
    }  

Best Regards