Introduce new tests for `ResponseInstruction::WithReplyPath`

- The new tests check both successful and unsuccessful `reply_path`
  creation conditions.

diff --git a/lightning/src/onion_message/functional_tests.rs b/lightning/src/onion_message/functional_tests.rs
index 0c2342ca15403f31a6bd7e35808951802bfd12bb..0c3c67d4483914c63beec442ab7efd7728cd9080 100644 (file)
--- a/lightning/src/onion_message/functional_tests.rs
+++ b/lightning/src/onion_message/functional_tests.rs
@@ -437,6 +437,73 @@ fn async_response_over_one_blinded_hop() {
        pass_along_path(&nodes);
 }
 
+#[test]
+fn async_response_with_reply_path_succeeds() {
+       // Simulate an asynchronous interaction between two nodes, Alice and Bob.
+       // Create a channel between the two nodes to establish them as announced nodes,
+       // which allows the creation of the reply_path for successful communication.
+
+       let mut nodes = create_nodes(2);
+       let alice = &nodes[0];
+       let bob = &nodes[1];
+       let secp_ctx = Secp256k1::new();
+
+       add_channel_to_graph(alice, bob, &secp_ctx, 24);
+
+       // Alice receives a message from Bob with an added reply_path for responding back.
+       let message = TestCustomMessage::Ping;
+       let path_id = Some([2; 32]);
+       let reply_path = BlindedPath::new_for_message(&[], bob.node_id, &*bob.entropy_source, &secp_ctx).unwrap();
+
+       // Alice asynchronously responds to Bob, expecting a response back from him.
+       let responder = Responder::new(reply_path, path_id);
+       alice.custom_message_handler.expect_message_and_response(message.clone());
+       let response_instruction = alice.custom_message_handler.handle_custom_message(message, Some(responder));
+
+       assert_eq!(
+               alice.messenger.handle_onion_message_response(response_instruction),
+               Ok(Some(SendSuccess::Buffered)),
+       );
+
+       // Set Bob's expectation and pass the Onion Message along the path.
+       bob.custom_message_handler.expect_message(TestCustomMessage::Pong);
+       pass_along_path(&nodes);
+
+       // Bob responds back to Alice using the reply_path she included with the OnionMessage.
+       // Set Alice's expectation and reverse the path for the response.
+       alice.custom_message_handler.expect_message(TestCustomMessage::Ping);
+       nodes.reverse();
+       pass_along_path(&nodes);
+}
+
+#[test]
+fn async_response_with_reply_path_fails() {
+       // Simulate an asynchronous interaction between two unannounced nodes, Alice and Bob.
+       // Since the nodes are unannounced, attempting to respond using a reply_path
+       // will fail, leading to an expected failure in communication.
+
+       let nodes = create_nodes(2);
+       let alice = &nodes[0];
+       let bob = &nodes[1];
+       let secp_ctx = Secp256k1::new();
+
+       // Alice receives a message from Bob with an added reply_path for responding back.
+       let message = TestCustomMessage::Ping;
+       let path_id = Some([2; 32]);
+       let reply_path = BlindedPath::new_for_message(&[], bob.node_id, &*bob.entropy_source, &secp_ctx).unwrap();
+
+       // Alice tries to asynchronously respond to Bob, but fails because the nodes are unannounced.
+       // Therefore, the reply_path cannot be used for the response.
+       let responder = Responder::new(reply_path, path_id);
+       alice.custom_message_handler.expect_message_and_response(message.clone());
+       let response_instruction = alice.custom_message_handler.handle_custom_message(message, Some(responder));
+
+       assert_eq!(
+               alice.messenger.handle_onion_message_response(response_instruction),
+               Err(SendError::PathNotFound),
+       );
+}
+
 #[test]
 fn too_big_packet_error() {
        // Make sure we error as expected if a packet is too big to send.