This tests the behavior when other references already exist. First we
check neither the document nor the image have any references yet:

  >>> doc = portal.doc1
  >>> self.assertEqual(doc.getReferences(), [])
  >>> self.assertEqual(doc.getBackReferences(), [])
  >>> img = portal.image1
  >>> self.assertEqual(img.getReferences(), [])
  >>> self.assertEqual(img.getBackReferences(), [])

Then establish a reference between the document and image as a related
item:

  >>> self.setRoles(('Manager',))
  >>> doc.setRelatedItems(img)

  >>> doc.getRelatedItems()
  [<ATImage at /plone/image1>]

Next edit the document body and insert a link to the image, which should
trigger the creation of a link integrity reference:

  >>> tag = img.tag()
  >>> self.setText(doc, tag)

  >>> from plone.app.linkintegrity.handlers import referencedRelationship
  >>> doc.getReferences(relationship=referencedRelationship)
  [<ATImage at /plone/image1>]

And the related item reference remains in place:

  >>> doc.getRelatedItems()
  [<ATImage at /plone/image1>]

Now edit the document body again with some link to the image, which
should leave both the references in place:

  >>> self.setText(doc, tag)
  >>> doc.getReferences(relationship=referencedRelationship)
  [<ATImage at /plone/image1>]

  >>> doc.getRelatedItems()
  [<ATImage at /plone/image1>]

Finally, edit the document body again, this time removing the link to the
image, which should trigger the removal of the link integrity reference:

  >>> self.setText(doc, 'where did my link go?')
  >>> doc.getReferences(relationship=referencedRelationship)
  []

And again the related item reference remains in place:

  >>> doc.getRelatedItems()
  [<ATImage at /plone/image1>]