Add a test of the new channel saturation limit

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 17253842e9214a871b177166557a9c06fd97698f..40cd439b1df261c6c1a4c433cf4ea892a0864448 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -5722,6 +5722,50 @@ mod tests {
                }
        }
 
+       #[test]
+       fn avoids_saturating_channels() {
+               let (secp_ctx, network_graph, gossip_sync, _, logger) = build_graph();
+               let (_, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
+
+               let scorer = ProbabilisticScorer::new(Default::default(), &*network_graph, Arc::clone(&logger));
+
+               // Set the fee on channel 13 to 100% to match channel 4 giving us two equivalent paths (us
+               // -> node 7 -> node2 and us -> node 1 -> node 2) which we should balance over.
+               update_channel(&gossip_sync, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
+                       chain_hash: genesis_block(Network::Testnet).header.block_hash(),
+                       short_channel_id: 4,
+                       timestamp: 2,
+                       flags: 0,
+                       cltv_expiry_delta: (4 << 4) | 1,
+                       htlc_minimum_msat: 0,
+                       htlc_maximum_msat: OptionalField::Present(200_000_000),
+                       fee_base_msat: 0,
+                       fee_proportional_millionths: 0,
+                       excess_data: Vec::new()
+               });
+               update_channel(&gossip_sync, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
+                       chain_hash: genesis_block(Network::Testnet).header.block_hash(),
+                       short_channel_id: 13,
+                       timestamp: 2,
+                       flags: 0,
+                       cltv_expiry_delta: (13 << 4) | 1,
+                       htlc_minimum_msat: 0,
+                       htlc_maximum_msat: OptionalField::Present(200_000_000),
+                       fee_base_msat: 0,
+                       fee_proportional_millionths: 0,
+                       excess_data: Vec::new()
+               });
+
+               let payment_params = PaymentParameters::from_node_id(nodes[2]).with_features(InvoiceFeatures::known());
+               let keys_manager = test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet);
+               let random_seed_bytes = keys_manager.get_secure_random_bytes();
+               // 150,000 sat is less than the available liquidity on each channel, set above.
+               let route = get_route(&our_id, &payment_params, &network_graph.read_only(), None, 150_000_000, 42, Arc::clone(&logger), &scorer, &random_seed_bytes).unwrap();
+               assert_eq!(route.paths.len(), 2);
+               assert!((route.paths[0][1].short_channel_id == 4 && route.paths[1][1].short_channel_id == 13) ||
+                       (route.paths[1][1].short_channel_id == 4 && route.paths[0][1].short_channel_id == 13));
+       }
+
        #[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.