Add PRUNE back and peer list verifier test.

tests/pubsub/testgossipsub.nim

@@ -1799,3 +1799,96 @@ suite "Gossipsub Parameters":
     # Cleanup
     await allFuturesThrowing(nodes.mapIt(allFutures(it.switch.stop())))
     await allFuturesThrowing(nodesFut)
+
+  asyncTest "Verify inclusion of backoff periods and peer lists in PRUNE messages for Peer Exchange":
+    # A, B & C are subscribed to something
+    # B unsubcribe from it, it should send
+    # PX to A & C
+    #
+    # C sent his SPR, not A
+    let
+      topic = "foobar"
+      nodes =
+        generateNodes(2, gossip = true, enablePX = true) &
+        generateNodes(1, gossip = true, sendSignedPeerRecord = true)
+
+      # start switches
+      nodesFut = await allFinished(
+        nodes[0].switch.start(), nodes[1].switch.start(), nodes[2].switch.start()
+      )
+
+    var
+      gossip0 = GossipSub(nodes[0])
+      gossip1 = GossipSub(nodes[1])
+      gossip2 = GossipSub(nodes[2])
+
+    # Connect nodes
+    await subscribeNodes(nodes)
+
+    # Subscribe nodes to the same topic
+    for node in nodes:
+      node.subscribe(topic, voidTopicHandler)
+
+    for x in 0 ..< 3:
+      for y in 0 ..< 3:
+        if x != y:
+          await waitSub(nodes[x], nodes[y], topic)
+
+    # Add an observer to node 2 for PRUNE messages
+    var receivedPrunes: seq[ControlPrune] = @[]
+    let checkForPrunes = proc(peer: PubSubPeer, msgs: var RPCMsg) =
+      if msgs.control.isSome:
+        let prunes = msgs.control.get.prune
+        for prune in prunes:
+          if prune.topicID == topic:
+            receivedPrunes.add(prune)
+
+    gossip2.addObserver(PubSubObserver(onRecv: checkForPrunes))
+
+    # Setup record handlers for all nodes
+    var
+      passed0: Future[void] = newFuture[void]()
+      passed1: Future[void] = newFuture[void]()
+      passed2: Future[void] = newFuture[void]()
+    gossip0.routingRecordsHandler.add(
+      proc(peer: PeerId, tag: string, peers: seq[RoutingRecordsPair]) =
+        check:
+          tag == topic
+          peers.len == 2
+          peers[0].record.isSome() xor peers[1].record.isSome()
+        passed0.complete()
+    )
+    gossip1.routingRecordsHandler.add(
+      proc(peer: PeerId, tag: string, peers: seq[RoutingRecordsPair]) =
+        passed1.complete()
+    )
+    gossip2.routingRecordsHandler.add(
+      proc(peer: PeerId, tag: string, peers: seq[RoutingRecordsPair]) =
+        check:
+          tag == topic
+          peers.len == 2
+          peers[0].record.isSome() xor peers[1].record.isSome()
+        passed2.complete()
+    )
+
+    # Unsubscribe from the topic
+    nodes[1].unsubscribe(topic, handler)
+
+    # Then verify what nodes receive the PX
+    check:
+      (await passed0.waitForResult()).isOk
+      not (await passed1.waitForResult()).isOk
+      (await passed2.waitForResult()).isOk
+
+    # And verify node 2 received the PRUNE message and it contains the backoff period and peer list
+    check:
+      receivedPrunes.len == 1
+      receivedPrunes[0].topicID == "foobar"
+      receivedPrunes[0].peers.len == 2
+      receivedPrunes[0].backoff == 1
+
+    await allFuturesThrowing(
+      nodes[0].switch.stop(), nodes[1].switch.stop(), nodes[2].switch.stop()
+    )
+
+    await allFuturesThrowing(nodesFut.concat())