pytest: Test LightningRpc and plugin command notification support

tests/plugins/countdown.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+
+from pyln.client import Plugin
+import time
+
+plugin = Plugin()
+
+
+@plugin.method("countdown")
+def countdown(count, plugin, request):
+    count = int(count)
+    for i in range(count):
+        time.sleep(0.1)
+        request.notify("{}/{}".format(i, count), "INFO")
+
+    return "Done"
+
+
+plugin.run()