Clean up long_mpp_route_test and mpp_cheaper_route_test

These tests are a bit annoying to deal with and ultimately work on
almost the same graph subset, so it makes sense to combine their
graph layout logic and then call it twice.

We do that here, combining them and also cleaning up the possible
paths as there actually are paths that the router could select
which don't meet the tests requirements.

Author: TheBlueMatt

lightning/src/routing/router.rs

@@ -5740,187 +5740,33 @@ mod tests {
 	}
 
 	#[test]
-	fn long_mpp_route_test() {
-		let (secp_ctx, network_graph, gossip_sync, _, logger) = build_graph();
-		let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
-		let scorer = ln_test_utils::TestScorer::new();
-		let random_seed_bytes = [42; 32];
-		let config = UserConfig::default();
-		let payment_params = PaymentParameters::from_node_id(nodes[3], 42)
-			.with_bolt11_features(channelmanager::provided_bolt11_invoice_features(&config))
-			.unwrap();
-
-		// We need a route consisting of 3 paths:
-		// From our node to node3 via {node0, node2}, {node7, node2, node4} and {node7, node2}.
-		// Note that these paths overlap (channels 5, 12, 13).
-		// We will route 300 sats.
-		// Each path will have 100 sats capacity, those channels which
-		// are used twice will have 200 sats capacity.
-
-		// Disable other potential paths.
-		update_channel(&gossip_sync, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 2,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 2,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 7,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 2,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-
-		// Path via {node0, node2} is channels {1, 3, 5}.
-		update_channel(&gossip_sync, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 1,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 3,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-
-		// Capacity of 200 sats because this channel will be used by 3rd path as well.
-		add_channel(&gossip_sync, &secp_ctx, &privkeys[2], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 5,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[3], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 5,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 3, // disable direction 1
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-
-		// Path via {node7, node2, node4} is channels {12, 13, 6, 11}.
-		// Add 100 sats to the capacities of {12, 13}, because these channels
-		// are also used for 3rd path. 100 sats for the rest. Total capacity: 100 sats.
-		update_channel(&gossip_sync, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 12,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 13,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 6,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
-			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 11,
-			timestamp: 2,
-			message_flags: 1, // Only must_be_one
-			channel_flags: 0,
-			cltv_expiry_delta: 0,
-			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 0,
-			fee_proportional_millionths: 0,
-			excess_data: Vec::new()
-		});
-
-		// Path via {node7, node2} is channels {12, 13, 5}.
-		// We already limited them to 200 sats (they are used twice for 100 sats).
-		// Nothing to do here.
-
+	fn mpp_tests() {
+		let secp_ctx = Secp256k1::new();
+		let (_, _, _, nodes) = get_nodes(&secp_ctx);
 		{
-			// Attempt to route more than available results in a failure.
-			let route_params = RouteParameters::from_payment_params_and_value(
-				payment_params.clone(), 350_000);
-			if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
-					&our_id, &route_params, &network_graph.read_only(), None, Arc::clone(&logger),
-					&scorer, &Default::default(), &random_seed_bytes) {
-						assert_eq!(err, "Failed to find a sufficient route to the given destination");
-			} else { panic!(); }
-		}
+			// Check that if we have two cheaper paths and a more expensive (fewer hops) path, we
+			// choose the two cheaper paths:
+			let route = do_mpp_route_tests(180_000).unwrap();
+			assert_eq!(route.paths.len(), 2);
 
+			let mut total_value_transferred_msat = 0;
+			let mut total_paid_msat = 0;
+			for path in &route.paths {
+				assert_eq!(path.hops.last().unwrap().pubkey, nodes[3]);
+				total_value_transferred_msat += path.final_value_msat();
+				for hop in &path.hops {
+					total_paid_msat += hop.fee_msat;
+				}
+			}
+			// If we paid fee, this would be higher.
+			assert_eq!(total_value_transferred_msat, 180_000);
+			let total_fees_paid = total_paid_msat - total_value_transferred_msat;
+			assert_eq!(total_fees_paid, 0);
+		}
 		{
-			// Now, attempt to route 300 sats (exact amount we can route).
-			// Our algorithm should provide us with these 3 paths, 100 sats each.
-			let route_params = RouteParameters::from_payment_params_and_value(
-				payment_params, 300_000);
-			let route = get_route(&our_id, &route_params, &network_graph.read_only(), None,
-				Arc::clone(&logger), &scorer, &Default::default(), &random_seed_bytes).unwrap();
+			// Check that if we use the same channels but need to send more than we could fit in
+			// the cheaper paths we select all three paths:
+			let route = do_mpp_route_tests(300_000).unwrap();
 			assert_eq!(route.paths.len(), 3);
 
 			let mut total_amount_paid_msat = 0;
@@ -5930,11 +5776,11 @@ mod tests {
 			}
 			assert_eq!(total_amount_paid_msat, 300_000);
 		}
-
+		// Check that trying to pay more than our available liquidity fails.
+		assert!(do_mpp_route_tests(300_001).is_err());
 	}
 
-	#[test]
-	fn mpp_cheaper_route_test() {
+	fn do_mpp_route_tests(amt: u64) -> Result<Route, LightningError> {
 		let (secp_ctx, network_graph, gossip_sync, _, logger) = build_graph();
 		let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
 		let scorer = ln_test_utils::TestScorer::new();
@@ -5944,21 +5790,17 @@ mod tests {
 			.with_bolt11_features(channelmanager::provided_bolt11_invoice_features(&config))
 			.unwrap();
 
-		// This test checks that if we have two cheaper paths and one more expensive path,
-		// so that liquidity-wise any 2 of 3 combination is sufficient,
-		// two cheaper paths will be taken.
-		// These paths have equal available liquidity.
-
-		// We need a combination of 3 paths:
-		// From our node to node3 via {node0, node2}, {node7, node2, node4} and {node7, node2}.
-		// Note that these paths overlap (channels 5, 12, 13).
-		// Each path will have 100 sats capacity, those channels which
-		// are used twice will have 200 sats capacity.
+		// Build a setup where we have three potential paths from us to node3:
+		//  {node0, node2, node4} (channels 1, 3, 6, 11), fee 0 msat,
+		//  {node7, node2, node4} (channels 12, 13, 6, 11), fee 0 msat, and
+		//  {node1} (channel 2, then a new channel 16), fee 1000 msat.
+		// Note that these paths overlap on channels 6 and 11.
+		// Each channel will have 100 sats capacity except for 6 and 11, which have 200.
 
 		// Disable other potential paths.
-		update_channel(&gossip_sync, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
+		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
 			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 2,
+			short_channel_id: 7,
 			timestamp: 2,
 			message_flags: 1, // Only must_be_one
 			channel_flags: 2,
@@ -5969,9 +5811,9 @@ mod tests {
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
 		});
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
+		update_channel(&gossip_sync, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
 			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 7,
+			short_channel_id: 4,
 			timestamp: 2,
 			message_flags: 1, // Only must_be_one
 			channel_flags: 2,
@@ -6011,31 +5853,30 @@ mod tests {
 			excess_data: Vec::new()
 		});
 
-		// Capacity of 200 sats because this channel will be used by 3rd path as well.
-		add_channel(&gossip_sync, &secp_ctx, &privkeys[2], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
-		update_channel(&gossip_sync, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
+		add_channel(&gossip_sync, &secp_ctx, &privkeys[1], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(16)), 16);
+		update_channel(&gossip_sync, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
 			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 5,
+			short_channel_id: 16,
 			timestamp: 2,
 			message_flags: 1, // Only must_be_one
 			channel_flags: 0,
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
+			htlc_maximum_msat: 100_000,
+			fee_base_msat: 1_000,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
 		});
 		update_channel(&gossip_sync, &secp_ctx, &privkeys[3], UnsignedChannelUpdate {
 			chain_hash: ChainHash::using_genesis_block(Network::Testnet),
-			short_channel_id: 5,
+			short_channel_id: 16,
 			timestamp: 2,
 			message_flags: 1, // Only must_be_one
 			channel_flags: 3, // disable direction 1
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
-			fee_base_msat: 0,
+			htlc_maximum_msat: 100_000,
+			fee_base_msat: 1_000,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
 		});
@@ -6051,7 +5892,7 @@ mod tests {
 			channel_flags: 0,
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
+			htlc_maximum_msat: 100_000,
 			fee_base_msat: 0,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
@@ -6064,7 +5905,7 @@ mod tests {
 			channel_flags: 0,
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 200_000,
+			htlc_maximum_msat: 100_000,
 			fee_base_msat: 0,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
@@ -6078,8 +5919,8 @@ mod tests {
 			channel_flags: 0,
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
-			fee_base_msat: 1_000,
+			htlc_maximum_msat: 200_000,
+			fee_base_msat: 0,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
 		});
@@ -6091,7 +5932,7 @@ mod tests {
 			channel_flags: 0,
 			cltv_expiry_delta: 0,
 			htlc_minimum_msat: 0,
-			htlc_maximum_msat: 100_000,
+			htlc_maximum_msat: 200_000,
 			fee_base_msat: 0,
 			fee_proportional_millionths: 0,
 			excess_data: Vec::new()
@@ -6101,29 +5942,11 @@ mod tests {
 		// We already limited them to 200 sats (they are used twice for 100 sats).
 		// Nothing to do here.
 
-		{
-			// Now, attempt to route 180 sats.
-			// Our algorithm should provide us with these 2 paths.
-			let route_params = RouteParameters::from_payment_params_and_value(
-				payment_params, 180_000);
-			let route = get_route(&our_id, &route_params, &network_graph.read_only(), None,
-				Arc::clone(&logger), &scorer, &Default::default(), &random_seed_bytes).unwrap();
-			assert_eq!(route.paths.len(), 2);
-
-			let mut total_value_transferred_msat = 0;
-			let mut total_paid_msat = 0;
-			for path in &route.paths {
-				assert_eq!(path.hops.last().unwrap().pubkey, nodes[3]);
-				total_value_transferred_msat += path.final_value_msat();
-				for hop in &path.hops {
-					total_paid_msat += hop.fee_msat;
-				}
-			}
-			// If we paid fee, this would be higher.
-			assert_eq!(total_value_transferred_msat, 180_000);
-			let total_fees_paid = total_paid_msat - total_value_transferred_msat;
-			assert_eq!(total_fees_paid, 0);
-		}
+		let route_params = RouteParameters::from_payment_params_and_value(
+			payment_params, amt);
+		let res = get_route(&our_id, &route_params, &network_graph.read_only(), None,
+			Arc::clone(&logger), &scorer, &Default::default(), &random_seed_bytes);
+		res
 	}
 
 	#[test]