Expand Test suite

- Expand testing to ensure proper serialise-deserialise round-trip for
all events.
- Expand a multi-Part payment test to ensure that all the channel ids &
  user channel ids are present in the PaymentClaimable event

Author: shaavan

lightning/src/ln/blinded_payment_tests.rs

@@ -240,8 +240,28 @@ fn mpp_to_one_hop_blinded_path() {
 		Some(payment_secret), ev.clone(), false, None);
 
 	let ev = remove_first_msg_event_to_node(&nodes[2].node.get_our_node_id(), &mut events);
-	pass_along_path(&nodes[0], expected_route[1], amt_msat, payment_hash.clone(),
+	let event = pass_along_path(&nodes[0], expected_route[1], amt_msat, payment_hash.clone(),
 		Some(payment_secret), ev.clone(), true, None);
+
+	match event.unwrap() {
+		Event::PaymentClaimable { mut via_channel_id_pairs, .. } => {
+			let channels = nodes[3].node.list_channels();
+
+			// Convert to HashSets for order-agnostic comparison
+			let expected_chan_ids: HashSet<_> = channels.iter().map(|d| d.channel_id).collect();
+			let expected_user_chan_ids: HashSet<_> = channels.iter().map(|d| d.user_channel_id).collect();
+
+			let actual_chan_ids: HashSet<_> = via_channel_id_pairs.iter().map(|(chan_id, _)| *chan_id).collect();
+			let actual_user_chan_ids: HashSet<_> = via_channel_id_pairs.iter()
+				.filter_map(|(_, user_id_opt)| *user_id_opt)
+				.collect();
+
+			assert_eq!(actual_chan_ids, expected_chan_ids);
+			assert_eq!(actual_user_chan_ids, expected_user_chan_ids);
+		}
+		_ => panic!("Unexpected event"),
+	}
+
 	claim_payment_along_route(
 		ClaimAlongRouteArgs::new(&nodes[0], expected_route, payment_preimage)
 	);

lightning/src/ln/channelmanager.rs

@@ -10925,7 +10925,18 @@ where
 		let events = core::cell::RefCell::new(Vec::new());
 		let event_handler = |event: events::Event| Ok(events.borrow_mut().push(event));
 		self.process_pending_events(&event_handler);
-		events.into_inner()
+		let collected_events = events.into_inner();
+
+		// To expand the coverage and make sure all events are properly serialised and deserialised,
+		// we test all generated events round-trip:
+		for event in &collected_events {
+			let ser = event.encode();
+			if let Some(deser) = events::Event::read(&mut &ser[..]).expect("event should deserialize") {
+				assert_eq!(&deser, event, "event should roundtrip correctly");
+			}
+		}
+
+		collected_events
 	}
 
 	#[cfg(feature = "_test_utils")]