'Make sure that navigation_index correctly parses the various position values that we might get from calls to
path_to_location'

def test_navigation_index(self):

    self.assertEqual(1, navigation_index('1'))
    self.assertEqual(10, navigation_index('10'))
    self.assertEqual(None, navigation_index(None))
    self.assertEqual(1, navigation_index('1_2'))
    self.assertEqual(5, navigation_index('5_2'))
    self.assertEqual(7, navigation_index('7_3_5_6_'))
