  
          # Ensure source 1 is updated, and everything else is as expected
          queryset = NullableForeignKeySource.objects.all()
          expected = [
              {'id': 1, 'name': u'source-1', 'target': None},
              {'id': 2, 'name': u'source-2', 'target': 'target-1'},
              {'id': 3, 'name': u'source-3', 'target': None}
 
</s> remove             {'name': u'source-1', 'target': None},
            {'name': u'source-2', 'target': 'target-1'},
            {'name': u'source-3', 'target': None},
 </s> add             {'id': 1, 'name': u'source-1', 'target': None},
            {'id': 2, 'name': u'source-2', 'target': 'target-1'},
            {'id': 3, 'name': u'source-3', 'target': None} </s> remove             {'name': u'source-1', 'target': None},
            {'name': u'source-2', 'target': 'target-1'},
            {'name': u'source-3', 'target': None},
 </s> add             {'id': 1, 'name': u'source-1', 'target': None},
            {'id': 2, 'name': u'source-2', 'target': 'target-1'},
            {'id': 3, 'name': u'source-3', 'target': None} </s> remove             {'name': u'source-1', 'target': 'target-1'},
            {'name': u'source-2', 'target': 'target-1'},
            {'name': u'source-3', 'target': None},
 </s> add             {'id': 1, 'name': u'source-1', 'target': 'target-1'},
            {'id': 2, 'name': u'source-2', 'target': 'target-1'},
            {'id': 3, 'name': u'source-3', 'target': None}, </s> remove             {'name': u'source-1', 'target': 'target-1'},
            {'name': u'source-2', 'target': 'target-1'},
            {'name': u'source-3', 'target': None},
            {'name': u'source-4', 'target': None}
 </s> add             {'id': 1, 'name': u'source-1', 'target': 'target-1'},
            {'id': 2, 'name': u'source-2', 'target': 'target-1'},
            {'id': 3, 'name': u'source-3', 'target': None},
            {'id': 4, 'name': u'source-4', 'target': None}
        serializer = NullableSlugSourceSerializer(queryset)
  
          # Ensure source 1 is updated, and everything else is as expected
          queryset = NullableForeignKeySource.objects.all()
        serializer = NullableSlugSourceSerializer(queryset)
          expected = [
              {'id': 1, 'name': u'source-1', 'target': None},
              {'id': 2, 'name': u'source-2', 'target': 'target-1'},
              {'id': 3, 'name': u'source-3', 'target': None}
keep keep add keep keep keep keep
 Drop bits of relations_slug tests which don't mirror existing tests. 
rest_framework/tests/relations_slug.py