diff --git a/protocols/gossipsub/src/behaviour/tests.rs b/protocols/gossipsub/src/behaviour/tests.rs
index 5413f6db..ab1deb32 100644
--- a/protocols/gossipsub/src/behaviour/tests.rs
+++ b/protocols/gossipsub/src/behaviour/tests.rs
@@ -222,17 +222,19 @@ where
         }
     };
 
-    #[allow(deprecated)]
     gs.on_swarm_event(FromSwarm::ConnectionEstablished(ConnectionEstablished {
         peer_id: peer,
-        connection_id: ConnectionId::DUMMY,
+        connection_id: ConnectionId::new_unchecked(0),
         endpoint: &endpoint,
         failed_addresses: &[],
         other_established: 0, // first connection
     }));
     if let Some(kind) = kind {
-        #[allow(deprecated)]
-        gs.on_connection_handler_event(peer, ConnectionId::DUMMY, HandlerEvent::PeerKind(kind));
+        gs.on_connection_handler_event(
+            peer,
+            ConnectionId::new_unchecked(0),
+            HandlerEvent::PeerKind(kind),
+        );
     }
     if explicit {
         gs.add_explicit_peer(&peer);
@@ -582,10 +584,9 @@ fn test_join() {
     for _ in 0..3 {
         let random_peer = PeerId::random();
         // inform the behaviour of a new peer
-        #[allow(deprecated)]
         gs.on_swarm_event(FromSwarm::ConnectionEstablished(ConnectionEstablished {
             peer_id: random_peer,
-            connection_id: ConnectionId::DUMMY,
+            connection_id: ConnectionId::new_unchecked(0),
             endpoint: &ConnectedPoint::Dialer {
                 address: "/ip4/127.0.0.1".parse::<Multiaddr>().unwrap(),
                 role_override: Endpoint::Dialer,
@@ -965,10 +966,7 @@ fn test_get_random_peers() {
                 *p,
                 PeerConnections {
                     kind: PeerKind::Gossipsubv1_1,
-                    connections: vec![
-                        #[allow(deprecated)]
-                        ConnectionId::DUMMY,
-                    ],
+                    connections: vec![ConnectionId::new_unchecked(0)],
                 },
             )
         })
@@ -2998,8 +2996,7 @@ fn test_ignore_rpc_from_peers_below_graylist_threshold() {
     //receive from p1
     gs.on_connection_handler_event(
         p1,
-        #[allow(deprecated)]
-        ConnectionId::DUMMY,
+        ConnectionId::new_unchecked(0),
         HandlerEvent::Message {
             rpc: Rpc {
                 messages: vec![raw_message1],
@@ -3025,8 +3022,7 @@ fn test_ignore_rpc_from_peers_below_graylist_threshold() {
     //receive from p2
     gs.on_connection_handler_event(
         p2,
-        #[allow(deprecated)]
-        ConnectionId::DUMMY,
+        ConnectionId::new_unchecked(0),
         HandlerEvent::Message {
             rpc: Rpc {
                 messages: vec![raw_message3],
@@ -3632,8 +3628,7 @@ fn test_scoring_p4_invalid_signature() {
 
     gs.on_connection_handler_event(
         peers[0],
-        #[allow(deprecated)]
-        ConnectionId::DUMMY,
+        ConnectionId::new_unchecked(0),
         HandlerEvent::Message {
             rpc: Rpc {
                 messages: vec![],
@@ -4114,11 +4109,10 @@ fn test_scoring_p6() {
     }
 
     //add additional connection for 3 others with addr
-    #[allow(deprecated)]
     for id in others.iter().take(3) {
         gs.on_swarm_event(FromSwarm::ConnectionEstablished(ConnectionEstablished {
             peer_id: *id,
-            connection_id: ConnectionId::DUMMY,
+            connection_id: ConnectionId::new_unchecked(0),
             endpoint: &ConnectedPoint::Dialer {
                 address: addr.clone(),
                 role_override: Endpoint::Dialer,
@@ -4137,10 +4131,9 @@ fn test_scoring_p6() {
 
     //add additional connection for 3 of the peers to addr2
     for peer in peers.iter().take(3) {
-        #[allow(deprecated)]
         gs.on_swarm_event(FromSwarm::ConnectionEstablished(ConnectionEstablished {
             peer_id: *peer,
-            connection_id: ConnectionId::DUMMY,
+            connection_id: ConnectionId::new_unchecked(0),
             endpoint: &ConnectedPoint::Dialer {
                 address: addr2.clone(),
                 role_override: Endpoint::Dialer,
@@ -4168,10 +4161,9 @@ fn test_scoring_p6() {
     );
 
     //two times same ip doesn't count twice
-    #[allow(deprecated)]
     gs.on_swarm_event(FromSwarm::ConnectionEstablished(ConnectionEstablished {
         peer_id: peers[0],
-        connection_id: ConnectionId::DUMMY,
+        connection_id: ConnectionId::new_unchecked(0),
         endpoint: &ConnectedPoint::Dialer {
             address: addr,
             role_override: Endpoint::Dialer,
@@ -5179,8 +5171,7 @@ fn test_subscribe_and_graft_with_negative_score() {
 
     let (mut gs2, _, _) = inject_nodes1().create_network();
 
-    #[allow(deprecated)]
-    let connection_id = ConnectionId::DUMMY;
+    let connection_id = ConnectionId::new_unchecked(0);
 
     let topic = Topic::new("test");
 
diff --git a/protocols/kad/src/behaviour/test.rs b/protocols/kad/src/behaviour/test.rs
index 33cd9dbe..f848812d 100644
--- a/protocols/kad/src/behaviour/test.rs
+++ b/protocols/kad/src/behaviour/test.rs
@@ -1295,8 +1295,7 @@ fn network_behaviour_on_address_change() {
     let local_peer_id = PeerId::random();
 
     let remote_peer_id = PeerId::random();
-    #[allow(deprecated)]
-    let connection_id = ConnectionId::DUMMY;
+    let connection_id = ConnectionId::new_unchecked(0);
     let old_address: Multiaddr = Protocol::Memory(1).into();
     let new_address: Multiaddr = Protocol::Memory(2).into();
 
diff --git a/swarm/CHANGELOG.md b/swarm/CHANGELOG.md
index c3dcb1ec..aea268e5 100644
--- a/swarm/CHANGELOG.md
+++ b/swarm/CHANGELOG.md
@@ -3,7 +3,11 @@
 - Deprecate `ConnectionLimits` in favor of `libp2p::connection_limits`.
   See [PR 3386].
 
+- Introduce `ConnectionId::new_unchecked` to allow for more sophisticated, manual tests of `NetworkBehaviour`.
+  See [PR 3652].
+
 [PR 3386]: https://github.com/libp2p/rust-libp2p/pull/3386
+[PR 3652]: https://github.com/libp2p/rust-libp2p/pull/3652
 
 # 0.42.0
 
diff --git a/swarm/src/connection.rs b/swarm/src/connection.rs
index 131f8715..e7e71fdf 100644
--- a/swarm/src/connection.rs
+++ b/swarm/src/connection.rs
@@ -67,6 +67,16 @@ impl ConnectionId {
     )]
     pub const DUMMY: ConnectionId = ConnectionId(0);
 
+    /// Creates an _unchecked_ [`ConnectionId`].
+    ///
+    /// [`Swarm`](crate::Swarm) enforces that [`ConnectionId`]s are unique and not reused.
+    /// This constructor does not, hence the _unchecked_.
+    ///
+    /// It is primarily meant for allowing manual tests of [`NetworkBehaviour`](crate::NetworkBehaviour)s.
+    pub fn new_unchecked(id: usize) -> Self {
+        Self(id)
+    }
+
     /// Returns the next available [`ConnectionId`].
     pub(crate) fn next() -> Self {
         Self(NEXT_CONNECTION_ID.fetch_add(1, Ordering::SeqCst))