def test_block_branch_not_changed_by_preview_handler(self, default_store):
        """
        Tests preview_handler should not update blocks being previewed
        """
        client = Client()
        client.login(username=self.user.username, password=self.user_password)

        with self.store.default_store(default_store):
            course = CourseFactory.create()

            block = ItemFactory.create(
                parent_location=course.location,
                category="problem"
            )

            url = reverse_usage_url(
                'preview_handler',
                block.location,
                kwargs={'handler': 'xmodule_handler/problem_check'}
            )
            response = client.post(url)
            self.assertEqual(response.status_code, 200)
            self.assertFalse(modulestore().has_changes(modulestore().get_item(block.location)))