PYTHON-1792 More reliable tests for ChangeStream.try_next

(cherry picked from commit 5ebd293)

Author: ShaneHarvey

test/test_change_stream.py

@@ -36,13 +36,13 @@
 from bson.py3compat import iteritems
 from bson.raw_bson import DEFAULT_RAW_BSON_OPTIONS, RawBSONDocument
 
-from pymongo import monitoring
 from pymongo.change_stream import _NON_RESUMABLE_GETMORE_ERRORS
 from pymongo.command_cursor import CommandCursor
 from pymongo.errors import (InvalidOperation, OperationFailure,
                             ServerSelectionTimeoutError)
 from pymongo.message import _CursorAddress
 from pymongo.read_concern import ReadConcern
+from pymongo.write_concern import WriteConcern
 
 from test import client_context, unittest, IntegrationTest
 from test.utils import (
@@ -70,10 +70,13 @@ def kill_change_stream_cursor(self, change_stream):
         client._close_cursor_now(cursor.cursor_id, address)
 
     def test_try_next(self):
-        coll = self.watched_collection()
+        # ChangeStreams only read majority committed data so use w:majority.
+        coll = self.watched_collection().with_options(
+            write_concern=WriteConcern("majority"))
+        coll.drop()
         coll.insert_one({})
         self.addCleanup(coll.drop)
-        with self.change_stream(max_await_time_ms=100) as stream:
+        with self.change_stream(max_await_time_ms=250) as stream:
             self.assertIsNone(stream.try_next())
             self.assertIsNone(stream._resume_token)
             coll.insert_one({})
@@ -88,14 +91,16 @@ def test_try_next_runs_one_getmore(self):
         # Connect to the cluster.
         client.admin.command('ping')
         listener.results.clear()
-        coll = self.watched_collection()
+        # ChangeStreams only read majority committed data so use w:majority.
+        coll = self.watched_collection().with_options(
+            write_concern=WriteConcern("majority"))
         coll.drop()
         # Create the watched collection before starting the change stream to
         # skip any "create" events.
         coll.insert_one({'_id': 1})
         self.addCleanup(coll.drop)
         with self.change_stream_with_client(
-                client, max_await_time_ms=100) as stream:
+                client, max_await_time_ms=250) as stream:
             self.assertEqual(listener.started_command_names(), ["aggregate"])
             listener.results.clear()