pytest: Reproduce issue #3403, sendpay notifications with no waiter

We clone the test above, but this time we don't attach waiters (they'd be racy
anyway), and we wait for the notification to be called. This fails, but is
fixed in the next two commits.

tests/plugins/sendpay_notifications.py

@@ -14,13 +14,13 @@ def init(configuration, options, plugin):
 
 @plugin.subscribe("sendpay_success")
 def notify_sendpay_success(plugin, sendpay_success):
-    plugin.log("receive a sendpay_success recored, id: {}, payment_hash: {}".format(sendpay_success['id'], sendpay_success['payment_hash']))
+    plugin.log("Received a sendpay_success: id={}, payment_hash={}".format(sendpay_success['id'], sendpay_success['payment_hash']))
     plugin.success_list.append(sendpay_success)
 
 
 @plugin.subscribe("sendpay_failure")
 def notify_sendpay_failure(plugin, sendpay_failure):
-    plugin.log("receive a sendpay_failure recored, id: {}, payment_hash: {}".format(sendpay_failure['data']['id'],
+    plugin.log("Received a sendpay_failure: id={}, payment_hash={}".format(sendpay_failure['data']['id'],
                sendpay_failure['data']['payment_hash']))
     plugin.failure_list.append(sendpay_failure)
 

tests/test_plugin.py

@@ -758,6 +758,32 @@ def test_sendpay_notifications(node_factory, bitcoind):
     assert results['sendpay_failure'][0] == err.value.error
 
 
+@pytest.mark.xfail(strict=True)
+def test_sendpay_notifications_nowaiter(node_factory):
+    opts = [{'plugin': os.path.join(os.getcwd(), 'tests/plugins/sendpay_notifications.py')},
+            {},
+            {'may_reconnect': False}]
+    l1, l2, l3 = node_factory.line_graph(3, opts=opts, wait_for_announce=True)
+    chanid23 = l2.get_channel_scid(l3)
+    amount = 10**8
+
+    payment_hash1 = l3.rpc.invoice(amount, "first", "desc")['payment_hash']
+    payment_hash2 = l3.rpc.invoice(amount, "second", "desc")['payment_hash']
+    route = l1.rpc.getroute(l3.info['id'], amount, 1)['route']
+
+    l1.rpc.sendpay(route, payment_hash1)
+    l1.daemon.wait_for_log(r'Received a sendpay_success')
+
+    l2.rpc.close(chanid23, 1)
+
+    l1.rpc.sendpay(route, payment_hash2)
+    l1.daemon.wait_for_log(r'Received a sendpay_failure')
+
+    results = l1.rpc.call('listsendpays_plugin')
+    assert len(results['sendpay_success']) == 1
+    assert len(results['sendpay_failure']) == 1
+
+
 def test_rpc_command_hook(node_factory):
     """Test the `sensitive_command` hook"""
     plugin = os.path.join(os.getcwd(), "tests/plugins/rpc_command.py")