Implement test for build_route_from_hops.

lightning/src/routing/router.rs

@@ -1831,7 +1831,7 @@ fn build_route_from_hops_internal<L: Deref>(
 #[cfg(test)]
 mod tests {
 	use routing::network_graph::{NetworkGraph, NetGraphMsgHandler, NodeId};
-	use routing::router::{get_route, add_random_cltv_offset, default_node_features,
+	use routing::router::{get_route, build_route_from_hops_internal, add_random_cltv_offset, default_node_features,
 		PaymentParameters, Route, RouteHint, RouteHintHop, RouteHop, RoutingFees,
 		DEFAULT_MAX_TOTAL_CLTV_EXPIRY_DELTA, MAX_PATH_LENGTH_ESTIMATE};
 	use routing::scoring::{ChannelUsage, Score};
@@ -5529,6 +5529,26 @@ mod tests {
 		assert!(path_plausibility.iter().all(|x| *x));
 	}
 
+	#[test]
+	fn builds_correct_path_from_hops() {
+		let (secp_ctx, network, _, _, logger) = build_graph();
+		let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
+		let network_graph = network.read_only();
+
+		let keys_manager = test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet);
+		let random_seed_bytes = keys_manager.get_secure_random_bytes();
+
+		let payment_params = PaymentParameters::from_node_id(nodes[3]);
+		let hops = [nodes[1], nodes[2], nodes[4], nodes[3]];
+		let route = build_route_from_hops_internal(&our_id, &hops, &payment_params,
+			 &network_graph, 100, 0, Arc::clone(&logger), &random_seed_bytes).unwrap();
+		let route_hop_pubkeys = route.paths[0].iter().map(|hop| hop.pubkey).collect::<Vec<_>>();
+		assert_eq!(hops.len(), route.paths[0].len());
+		for (idx, hop_pubkey) in hops.iter().enumerate() {
+			assert!(*hop_pubkey == route_hop_pubkeys[idx]);
+		}
+	}
+
 	#[cfg(not(feature = "no-std"))]
 	pub(super) fn random_init_seed() -> u64 {
 		// Because the default HashMap in std pulls OS randomness, we can use it as a (bad) RNG.