test: add docker-compose with mosquitto and python subscriber

test/subscribe.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+import os
+import sys
+import time
+import paho.mqtt.client as mqtt
+
+broker = os.getenv('MQTT_BROKER', 'localhost:1883')
+topic = os.getenv('MQTT_TOPIC', 'lambdaiot')
+
+if broker.startswith('tcp://'):
+    broker = broker[len('tcp://'):]
+
+host, sep, port = broker.partition(':')
+port = int(port) if sep else 1883
+
+def on_connect(client, userdata, flags, rc):
+    print(f"Connected with result code {rc}")
+    client.subscribe(topic)
+    print(f"Subscribed to {topic}")
+
+def on_message(client, userdata, msg):
+    try:
+        payload = msg.payload.decode()
+    except Exception:
+        payload = str(msg.payload)
+    print(f"[{msg.topic}] {payload}")
+
+client = mqtt.Client()
+client.on_connect = on_connect
+client.on_message = on_message
+
+try:
+    client.connect(host, port, 60)
+except Exception as e:
+    print("Could not connect to broker:", e)
+    sys.exit(1)
+
+client.loop_forever()