PYTHON-3468 Test failures in test_srv_polling.TestSrvPolling (#1073)

Author: blink1073

test/test_srv_polling.py

@@ -130,7 +130,14 @@ def assert_nodelist_nochange(self, expected_nodelist, client):
         (WAIT_TIME * 10) seconds. Also check that the resolver is called at
         least once.
         """
-        sleep(WAIT_TIME * 10)
+
+        def predicate():
+            if set(expected_nodelist) == set(self.get_nodelist(client)):
+                return pymongo.srv_resolver._SrvResolver.get_hosts_and_min_ttl.call_count >= 1
+            return False
+
+        wait_until(predicate, "Node list equals expected nodelist", timeout=100 * WAIT_TIME)
+
         nodelist = self.get_nodelist(client)
         if set(expected_nodelist) != set(nodelist):
             msg = "Client nodelist %s changed unexpectedly (expected %s)"