add unit test

Author: vladak

tests/test_loop.py

@@ -68,6 +68,24 @@ def test_loop_basic(self) -> None:
                 assert ret_code == expected_rc
                 expected_rc += 1
 
+    def test_loop_timeout_vs_socket_timeout(self):
+        """
+        loop() should throw MMQTTException if the timeout argument is bigger than the socket timeout.
+        """
+        mqtt_client = MQTT.MQTT(
+            broker="127.0.0.1",
+            port=1883,
+            socket_pool=socket,
+            ssl_context=ssl.create_default_context(),
+            socket_timeout=1
+        )
+
+        mqtt_client.is_connected = lambda: True
+        with self.assertRaises(MQTT.MMQTTException) as context:
+            mqtt_client.loop(timeout=0.5)
+
+        assert "loop timeout" in str(context.exception)
+
     def test_loop_is_connected(self):
         """
         loop() should throw MMQTTException if not connected