PYTHON-2948 Add prose test for SRV polling with a custom service name (#764)

Author: juliusgeo

test/test_srv_polling.py

@@ -289,6 +289,24 @@ def test_does_not_flipflop(self):
             new = set(client.topology_description.server_descriptions())
             self.assertSetEqual(old, new)
 
+    def test_srv_service_name(self):
+        # Construct a valid final response callback distinct from base.
+        response = [
+            ("localhost.test.build.10gen.cc.", 27019),
+            ("localhost.test.build.10gen.cc.", 27020)
+        ]
+
+        def nodelist_callback():
+            return response
+
+        with SrvPollingKnobs(
+                ttl_time=WAIT_TIME, min_srv_rescan_interval=WAIT_TIME):
+            client = MongoClient(
+                "mongodb+srv://test22.test.build.10gen.cc/?srvServiceName"
+                "=customname")
+            with SrvPollingKnobs(nodelist_callback=nodelist_callback):
+                self.assert_nodelist_change(response, client)
+
 
 if __name__ == '__main__':
     unittest.main()