tests: Move clear_client_event_queues_for_testing to ZulipTestCase.

Following recent testing flakes that were traced down to this not
having been called causing `receiver_is_off_zulip` to depend on test
ordering, it makes sense to centralize this.

I think it should always have been in ZulipTestCase; it appears the
reason it wasn't from the beginning was that originally only
test_events.py interacted with it, and do_test there still needs to
call this directly (because it can be called multiple times within a
single test).  And then we did the wrong thing as expanded use of
Tornado event_queue code in tests to more of the codebase.

zerver/lib/test_classes.py

@@ -51,10 +51,9 @@ from zerver.models import (
     Subscription,
     UserProfile,
 )
-
 from zilencer.models import get_remote_server_by_uuid
 from zerver.decorator import do_two_factor_login
-
+from zerver.tornado.event_queue import clear_client_event_queues_for_testing
 
 import base64
 import mock
@@ -91,6 +90,11 @@ class ZulipTestCase(TestCase):
     # Ensure that the test system just shows us diffs
     maxDiff = None  # type: Optional[int]
 
+    def tearDown(self) -> None:
+        super().tearDown()
+        # Important: we need to clear event queues to avoid leaking data to future tests.
+        clear_client_event_queues_for_testing()
+
     '''
     WRAPPER_COMMENT:
 

zerver/tests/test_event_queue.py

@@ -10,7 +10,7 @@ from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.test_helpers import POSTRequestMock
 from zerver.models import Recipient, Stream, Subscription, UserProfile, get_stream
 from zerver.tornado.event_queue import maybe_enqueue_notifications, \
-    allocate_client_descriptor, process_message_event, clear_client_event_queues_for_testing, \
+    allocate_client_descriptor, process_message_event, \
     get_client_descriptor, missedmessage_hook
 from zerver.tornado.views import get_events
 
@@ -139,8 +139,6 @@ class MissedMessageNotificationsTest(ZulipTestCase):
 
         self.unsubscribe(hamlet, stream_name)
 
-        clear_client_event_queues_for_testing()
-
         queue_data = dict(
             all_public_streams=True,
             apply_markdown=True,

zerver/tests/test_events.py

@@ -160,11 +160,6 @@ class LogEventsTest(ZulipTestCase):
 
 
 class EventsEndpointTest(ZulipTestCase):
-    def tearDown(self) -> None:
-        super().tearDown()
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        clear_client_event_queues_for_testing()
-
     def test_events_register_endpoint(self) -> None:
 
         # This test is intended to get minimal coverage on the
@@ -270,11 +265,6 @@ class EventsEndpointTest(ZulipTestCase):
         self.assert_json_success(result)
 
 class GetEventsTest(ZulipTestCase):
-    def tearDown(self) -> None:
-        super().tearDown()
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        clear_client_event_queues_for_testing()
-
     def tornado_call(self, view_func: Callable[[HttpRequest, UserProfile], HttpResponse],
                      user_profile: UserProfile,
                      post_data: Dict[str, Any]) -> HttpResponse:
@@ -458,11 +448,6 @@ class GetEventsTest(ZulipTestCase):
         self.assertEqual(message["avatar_url"], None)
 
 class EventsRegisterTest(ZulipTestCase):
-    def tearDown(self) -> None:
-        super().tearDown()
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        clear_client_event_queues_for_testing()
-
     def setUp(self) -> None:
         super().setUp()
         self.user_profile = self.example_user('hamlet')
@@ -487,7 +472,7 @@ class EventsRegisterTest(ZulipTestCase):
         '''
         Make sure we have a clean slate of client descriptors for these tests.
         If we don't do this, then certain failures will only manifest when you
-        run multiple tests.
+        run multiple tests within a single test function.
         '''
         clear_client_event_queues_for_testing()
 
@@ -2755,11 +2740,6 @@ class EventQueueTest(TestCase):
                            "timestamp": "1"}])
 
 class ClientDescriptorsTest(ZulipTestCase):
-    def tearDown(self) -> None:
-        super().tearDown()
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        clear_client_event_queues_for_testing()
-
     def test_get_client_info_for_all_public_streams(self) -> None:
         hamlet = self.example_user('hamlet')
         realm = hamlet.realm

zerver/tests/test_tornado.py

@@ -50,8 +50,6 @@ class TornadoWebTestCase(AsyncHTTPTestCase, ZulipTestCase):
     def tearDown(self) -> None:
         super().tearDown()
         self.session_cookie = None  # type: Optional[Dict[str, str]]
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        event_queue.clear_client_event_queues_for_testing()
 
     @override_settings(DEBUG=False)
     def get_app(self) -> Application:
@@ -143,7 +141,6 @@ class EventsTestCase(TornadoWebTestCase):
         self.assertEqual(data['result'], 'success')
 
 class WebSocketBaseTestCase(AsyncHTTPTestCase, ZulipTestCase):
-
     def setUp(self) -> None:
         settings.RUNNING_INSIDE_TORNADO = True
         super().setUp()
@@ -151,8 +148,6 @@ class WebSocketBaseTestCase(AsyncHTTPTestCase, ZulipTestCase):
     def tearDown(self) -> None:
         super().tearDown()
         settings.RUNNING_INSIDE_TORNADO = False
-        # Important: we need to clear event queues to avoid leaking data to future tests.
-        event_queue.clear_client_event_queues_for_testing()
 
     @gen.coroutine
     def ws_connect(self, path: str, cookie_header: str,