Add unit test for last_rapid_gossip_sync_timestamp field [de]serialization.

Author: arik-so

lightning/src/routing/network_graph.rs

@@ -2370,6 +2370,18 @@ mod tests {
 		assert!(<NetworkGraph>::read(&mut io::Cursor::new(&w.0)).unwrap() == network_graph);
 	}
 
+	#[test]
+	fn network_graph_tlv_serialization() {
+		let mut network_graph = create_network_graph();
+		network_graph.last_rapid_gossip_sync_timestamp.replace(42);
+
+		let mut w = test_utils::TestVecWriter(Vec::new());
+		network_graph.write(&mut w).unwrap();
+		let reassembled_network_graph: NetworkGraph = Readable::read(&mut io::Cursor::new(&w.0)).unwrap();
+		assert!(reassembled_network_graph == network_graph);
+		assert_eq!(reassembled_network_graph.last_rapid_gossip_sync_timestamp.unwrap(), 42);
+	}
+
 	#[test]
 	#[cfg(feature = "std")]
 	fn calling_sync_routing_table() {