test: Make pytz api related tests more resilient.

Compare the output of our API with the library that backs them so that
we don't have brittle tests that need to be updated when the number of
timezones changes.

openedx/core/djangoapps/user_api/tests/test_views.py

@@ -5,7 +5,7 @@ import ddt
 from django.test.utils import override_settings
 from django.urls import reverse
 from opaque_keys.edx.keys import CourseKey
-from pytz import common_timezones_set
+from pytz import common_timezones_set, common_timezones, country_timezones
 
 from openedx.core.djangoapps.django_comment_common import models
 from openedx.core.djangolib.testing.utils import CacheIsolationTestCase, skip_unless_lms
@@ -634,13 +634,16 @@ class CountryTimeZoneListViewTest(UserApiTestCase):
         assert time_zone_name in common_timezones_set
         assert time_zone_info['description'] == get_display_time_zone(time_zone_name)
 
-    # The time zones count may need to change each time we upgrade pytz
-    @ddt.data((ALL_TIME_ZONES_URI, 432),
-              (COUNTRY_TIME_ZONES_URI, 23))
-    @ddt.unpack
-    def test_get_basic(self, country_uri, expected_count):
+    def test_get_country_timezones(self):
         """ Verify that correct time zone info is returned """
-        results = self.get_json(country_uri)
-        assert len(results) == expected_count
+        results = self.get_json(self.COUNTRY_TIME_ZONES_URI)
+        assert len(results) == len(country_timezones['cA'])
+        for time_zone_info in results:
+            self._assert_time_zone_is_valid(time_zone_info)
+
+    def test_get_all_common_timezones(self):
+        """ Verify that correct time zone info is returned """
+        results = self.get_json(self.ALL_TIME_ZONES_URI)
+        assert len(results) == len(common_timezones)
         for time_zone_info in results:
             self._assert_time_zone_is_valid(time_zone_info)