def test_translate_locator(self):
        """
        tests translate_locator_to_location(BlockUsageLocator)
        """
        # lookup for non-existent course
        org = 'foo_org'
        course = 'bar_course'
        run = 'baz_run'
        new_style_org = '{}.geek_dept'.format(org)
        new_style_offering = '{}.{}'.format(course, run)
        prob_course_key = CourseLocator(
            org=new_style_org, offering=new_style_offering,
            branch='published',
        )
        prob_locator = BlockUsageLocator(
            prob_course_key,
            block_type='problem',
            block_id='problem2',
        )
        prob_location = loc_mapper().translate_locator_to_location(prob_locator)
        self.assertIsNone(prob_location, 'found entry in empty map table')

        loc_mapper().create_map_entry(
            SlashSeparatedCourseKey(org, course, run),
            new_style_org, new_style_offering,
            block_map={
                'abc123': {'problem': 'problem2'},
                '48f23a10395384929234': {'chapter': 'chapter48f'},
                'baz_run': {'course': 'root'},
            }
        )
        # only one course matches
        prob_location = loc_mapper().translate_locator_to_location(prob_locator)
        # default branch
        self.assertEqual(prob_location, Location(org, course, run, 'problem', 'abc123', None))
        # test get_course keyword
        prob_location = loc_mapper().translate_locator_to_location(prob_locator, get_course=True)
        self.assertEqual(prob_location, SlashSeparatedCourseKey(org, course, run))
        # explicit branch
        prob_locator = prob_locator.for_branch('draft')
        prob_location = loc_mapper().translate_locator_to_location(prob_locator)
        # Even though the problem was set as draft, we always return revision=None to work
        # with old mongo/draft modulestores.
        self.assertEqual(prob_location, Location(org, course, run, 'problem', 'abc123', None))
        prob_locator = BlockUsageLocator(
            prob_course_key.for_branch('production'),
            block_type='problem', block_id='problem2'
        )
        prob_location = loc_mapper().translate_locator_to_location(prob_locator)
        self.assertEqual(prob_location, Location(org, course, run, 'problem', 'abc123', None))
        # same for chapter except chapter cannot be draft in old system
        chap_locator = BlockUsageLocator(
            prob_course_key.for_branch('production'),
            block_type='chapter', block_id='chapter48f',
        )
        chap_location = loc_mapper().translate_locator_to_location(chap_locator)
        self.assertEqual(chap_location, Location(org, course, run, 'chapter', '48f23a10395384929234'))
        # explicit branch
        chap_locator = chap_locator.for_branch('draft')
        chap_location = loc_mapper().translate_locator_to_location(chap_locator)
        self.assertEqual(chap_location, Location(org, course, run, 'chapter', '48f23a10395384929234'))
        chap_locator = BlockUsageLocator(
            prob_course_key.for_branch('production'), block_type='chapter', block_id='chapter48f'
        )
        chap_location = loc_mapper().translate_locator_to_location(chap_locator)
        self.assertEqual(chap_location, Location(org, course, run, 'chapter', '48f23a10395384929234'))

        # look for non-existent problem
        prob_locator2 = BlockUsageLocator(
            prob_course_key.for_branch('draft'),
            block_type='problem', block_id='problem3'
        )
        prob_location = loc_mapper().translate_locator_to_location(prob_locator2)
        self.assertIsNone(prob_location, 'Found non-existent problem')

        # add a distractor course
        delta_run = 'delta_run'
        new_style_offering = '{}.{}'.format(course, delta_run)
        loc_mapper().create_map_entry(
            SlashSeparatedCourseKey(org, course, delta_run),
            new_style_org, new_style_offering,
            block_map={'abc123': {'problem': 'problem3'}}
        )
        prob_location = loc_mapper().translate_locator_to_location(prob_locator)
        self.assertEqual(prob_location, Location(org, course, run, 'problem', 'abc123', None))