chore(gossipsub): improve test structure

Improve gossipsub behavior tests structure.
Split the already big enough file into multiple test files according to their `Behaviour` tests  category.
Document the shared test primitives and rename structures, `InjectNodes` to `BehaviourTestBuilder` and remove the `inject_nodes` functions to use `Default`.

This will help with the new tests for partial messages on sigp#577 which will be eventually moved here

Pull-Request: #6232.

Author: jxs

protocols/gossipsub/src/behaviour/tests.rs

@@ -0,0 +1,387 @@
+// Copyright 2025 Sigma Prime Pty Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! Tests for explicit peer handling.
+
+use std::collections::BTreeSet;
+
+use libp2p_identity::PeerId;
+use libp2p_swarm::ToSwarm;
+
+use super::{count_control_msgs, disconnect_peer, flush_events, DefaultBehaviourTestBuilder};
+use crate::{
+    config::{Config, ConfigBuilder},
+    types::{Prune, RawMessage, RpcOut, Subscription, SubscriptionAction},
+    IdentTopic as Topic,
+};
+
+/// tests that a peer added as explicit peer gets connected to
+#[test]
+fn test_explicit_peer_gets_connected() {
+    let (mut gs, _, _, _) = DefaultBehaviourTestBuilder::default()
+        .peer_no(0)
+        .topics(Vec::new())
+        .to_subscribe(true)
+        .create_network();
+
+    // create new peer
+    let peer = PeerId::random();
+
+    // add peer as explicit peer
+    gs.add_explicit_peer(&peer);
+
+    let num_events = gs
+        .events
+        .iter()
+        .filter(|e| match e {
+            ToSwarm::Dial { opts } => opts.get_peer_id() == Some(peer),
+            _ => false,
+        })
+        .count();
+
+    assert_eq!(
+        num_events, 1,
+        "There was no dial peer event for the explicit peer"
+    );
+}
+
+#[test]
+fn test_explicit_peer_reconnects() {
+    let config = ConfigBuilder::default()
+        .check_explicit_peers_ticks(2)
+        .build()
+        .unwrap();
+    let (mut gs, others, queues, _) = DefaultBehaviourTestBuilder::default()
+        .peer_no(1)
+        .topics(Vec::new())
+        .to_subscribe(true)
+        .gs_config(config)
+        .create_network();
+
+    let peer = others.first().unwrap();
+
+    // add peer as explicit peer
+    gs.add_explicit_peer(peer);
+
+    flush_events(&mut gs, queues);
+
+    // disconnect peer
+    disconnect_peer(&mut gs, peer);
+
+    gs.heartbeat();
+
+    // check that no reconnect after first heartbeat since `explicit_peer_ticks == 2`
+    assert_eq!(
+        gs.events
+            .iter()
+            .filter(|e| match e {
+                ToSwarm::Dial { opts } => opts.get_peer_id() == Some(*peer),
+                _ => false,
+            })
+            .count(),
+        0,
+        "There was a dial peer event before explicit_peer_ticks heartbeats"
+    );
+
+    gs.heartbeat();
+
+    // check that there is a reconnect after second heartbeat
+    assert!(
+        gs.events
+            .iter()
+            .filter(|e| match e {
+                ToSwarm::Dial { opts } => opts.get_peer_id() == Some(*peer),
+                _ => false,
+            })
+            .count()
+            >= 1,
+        "There was no dial peer event for the explicit peer"
+    );
+}
+
+#[test]
+fn test_handle_graft_explicit_peer() {
+    let (mut gs, peers, queues, topic_hashes) = DefaultBehaviourTestBuilder::default()
+        .peer_no(1)
+        .topics(vec![String::from("topic1"), String::from("topic2")])
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    let peer = peers.first().unwrap();
+
+    gs.handle_graft(peer, topic_hashes.clone());
+
+    // peer got not added to mesh
+    assert!(gs.mesh[&topic_hashes[0]].is_empty());
+    assert!(gs.mesh[&topic_hashes[1]].is_empty());
+
+    // check prunes
+    let (control_msgs, _) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == peer
+            && match m {
+                RpcOut::Prune(Prune { topic_hash, .. }) => {
+                    topic_hash == &topic_hashes[0] || topic_hash == &topic_hashes[1]
+                }
+                _ => false,
+            }
+    });
+    assert!(
+        control_msgs >= 2,
+        "Not enough prunes sent when grafting from explicit peer"
+    );
+}
+
+#[test]
+fn explicit_peers_not_added_to_mesh_on_receiving_subscription() {
+    let (gs, peers, queues, topic_hashes) = DefaultBehaviourTestBuilder::default()
+        .peer_no(2)
+        .topics(vec![String::from("topic1")])
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    // only peer 1 is in the mesh not peer 0 (which is an explicit peer)
+    assert_eq!(
+        gs.mesh[&topic_hashes[0]],
+        vec![peers[1]].into_iter().collect()
+    );
+
+    // assert that graft gets created to non-explicit peer
+    let (control_msgs, queues) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[1] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert!(
+        control_msgs >= 1,
+        "No graft message got created to non-explicit peer"
+    );
+
+    // assert that no graft gets created to explicit peer
+    let (control_msgs, _) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[0] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert_eq!(
+        control_msgs, 0,
+        "A graft message got created to an explicit peer"
+    );
+}
+
+#[test]
+fn do_not_graft_explicit_peer() {
+    let (mut gs, others, queues, topic_hashes) = DefaultBehaviourTestBuilder::default()
+        .peer_no(1)
+        .topics(vec![String::from("topic")])
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    gs.heartbeat();
+
+    // mesh stays empty
+    assert_eq!(gs.mesh[&topic_hashes[0]], BTreeSet::new());
+
+    // assert that no graft gets created to explicit peer
+    let (control_msgs, _) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &others[0] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert_eq!(
+        control_msgs, 0,
+        "A graft message got created to an explicit peer"
+    );
+}
+
+#[test]
+fn do_forward_messages_to_explicit_peers() {
+    let (mut gs, peers, queues, topic_hashes) = DefaultBehaviourTestBuilder::default()
+        .peer_no(2)
+        .topics(vec![String::from("topic1"), String::from("topic2")])
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    let local_id = PeerId::random();
+
+    let message = RawMessage {
+        source: Some(peers[1]),
+        data: vec![12],
+        sequence_number: Some(0),
+        topic: topic_hashes[0].clone(),
+        signature: None,
+        key: None,
+        validated: true,
+    };
+    gs.handle_received_message(message.clone(), &local_id);
+    assert_eq!(
+        queues.into_iter().fold(0, |mut fwds, (peer_id, mut queue)| {
+            while !queue.is_empty() {
+                if matches!(queue.try_pop(), Some(RpcOut::Forward{message: m, ..}) if peer_id == peers[0] && m.data == message.data) {
+                    fwds +=1;
+                }
+            }
+            fwds
+        }),
+        1,
+        "The message did not get forwarded to the explicit peer"
+    );
+}
+
+#[test]
+fn explicit_peers_not_added_to_mesh_on_subscribe() {
+    let (mut gs, peers, queues, _) = DefaultBehaviourTestBuilder::default()
+        .peer_no(2)
+        .topics(Vec::new())
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    // create new topic, both peers subscribing to it but we do not subscribe to it
+    let topic = Topic::new(String::from("t"));
+    let topic_hash = topic.hash();
+    for peer in peers.iter().take(2) {
+        gs.handle_received_subscriptions(
+            &[Subscription {
+                action: SubscriptionAction::Subscribe,
+                topic_hash: topic_hash.clone(),
+            }],
+            peer,
+        );
+    }
+
+    // subscribe now to topic
+    gs.subscribe(&topic).unwrap();
+
+    // only peer 1 is in the mesh not peer 0 (which is an explicit peer)
+    assert_eq!(gs.mesh[&topic_hash], vec![peers[1]].into_iter().collect());
+
+    // assert that graft gets created to non-explicit peer
+    let (control_msgs, queues) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[1] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert!(
+        control_msgs > 0,
+        "No graft message got created to non-explicit peer"
+    );
+
+    // assert that no graft gets created to explicit peer
+    let (control_msgs, _) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[0] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert_eq!(
+        control_msgs, 0,
+        "A graft message got created to an explicit peer"
+    );
+}
+
+#[test]
+fn explicit_peers_not_added_to_mesh_from_fanout_on_subscribe() {
+    let (mut gs, peers, queues, _) = DefaultBehaviourTestBuilder::default()
+        .peer_no(2)
+        .topics(Vec::new())
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    // create new topic, both peers subscribing to it but we do not subscribe to it
+    let topic = Topic::new(String::from("t"));
+    let topic_hash = topic.hash();
+    for peer in peers.iter().take(2) {
+        gs.handle_received_subscriptions(
+            &[Subscription {
+                action: SubscriptionAction::Subscribe,
+                topic_hash: topic_hash.clone(),
+            }],
+            peer,
+        );
+    }
+
+    // we send a message for this topic => this will initialize the fanout
+    gs.publish(topic.clone(), vec![1, 2, 3]).unwrap();
+
+    // subscribe now to topic
+    gs.subscribe(&topic).unwrap();
+
+    // only peer 1 is in the mesh not peer 0 (which is an explicit peer)
+    assert_eq!(gs.mesh[&topic_hash], vec![peers[1]].into_iter().collect());
+
+    // assert that graft gets created to non-explicit peer
+    let (control_msgs, queues) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[1] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert!(
+        control_msgs >= 1,
+        "No graft message got created to non-explicit peer"
+    );
+
+    // assert that no graft gets created to explicit peer
+    let (control_msgs, _) = count_control_msgs(queues, |peer_id, m| {
+        peer_id == &peers[0] && matches!(m, RpcOut::Graft { .. })
+    });
+    assert_eq!(
+        control_msgs, 0,
+        "A graft message got created to an explicit peer"
+    );
+}
+
+#[test]
+fn no_gossip_gets_sent_to_explicit_peers() {
+    let (mut gs, peers, mut queues, topic_hashes) = DefaultBehaviourTestBuilder::default()
+        .peer_no(2)
+        .topics(vec![String::from("topic1"), String::from("topic2")])
+        .to_subscribe(true)
+        .gs_config(Config::default())
+        .explicit(1)
+        .create_network();
+
+    let local_id = PeerId::random();
+
+    let message = RawMessage {
+        source: Some(peers[1]),
+        data: vec![],
+        sequence_number: Some(0),
+        topic: topic_hashes[0].clone(),
+        signature: None,
+        key: None,
+        validated: true,
+    };
+
+    // forward the message
+    gs.handle_received_message(message, &local_id);
+
+    // simulate multiple gossip calls (for randomness)
+    for _ in 0..3 {
+        gs.emit_gossip();
+    }
+
+    // assert that no gossip gets sent to explicit peer
+    let mut receiver_queue = queues.remove(&peers[0]).unwrap();
+    let mut gossips = 0;
+    while !receiver_queue.is_empty() {
+        if let Some(RpcOut::IHave(_)) = receiver_queue.try_pop() {
+            gossips += 1;
+        }
+    }
+    assert_eq!(gossips, 0, "Gossip got emitted to explicit peer");
+}