WIP Create a MockedClientHandle helper type

Used to create and then track a mock `Client` instance.

zebra-network/src/peer_set/set.rs

@@ -86,6 +86,9 @@ use crate::{
     AddressBook, BoxError, Config,
 };
 
+#[cfg(test)]
+mod tests;
+
 /// A signal sent by the [`PeerSet`] when it has no ready peers, and gets a request from Zebra.
 ///
 /// In response to this signal, the crawler tries to open more peer connections.

zebra-network/src/peer_set/set/tests.rs

@@ -0,0 +1,51 @@
+use futures::channel::{mpsc, oneshot};
+use proptest::prelude::*;
+
+use crate::{
+    peer::{Client, ClientRequest, ErrorSlot, LoadTrackedClient},
+    protocol::external::types::Version,
+};
+
+/// A handle to a mocked [`Client`] instance.
+struct MockedClientHandle {
+    request_receiver: mpsc::Receiver<ClientRequest>,
+    shutdown_receiver: oneshot::Receiver<()>,
+    version: Version,
+}
+
+impl MockedClientHandle {
+    /// Create a new mocked [`Client`] instance, returning it together with a handle to track it.
+    pub fn new(version: Version) -> (Self, LoadTrackedClient) {
+        let (shutdown_sender, shutdown_receiver) = oneshot::channel();
+        let (request_sender, request_receiver) = mpsc::channel(1);
+
+        let client = Client {
+            shutdown_tx: Some(shutdown_sender),
+            server_tx: request_sender,
+            error_slot: ErrorSlot::default(),
+            version,
+        };
+
+        let handle = MockedClientHandle {
+            request_receiver,
+            shutdown_receiver,
+            version,
+        };
+
+        (handle, client.into())
+    }
+
+    /// Gets the peer protocol version associated to the [`Client`].
+    pub fn version(&self) -> Version {
+        self.version
+    }
+
+    /// Checks if the [`Client`] instance has not been dropped, which would have disconnected from
+    /// the peer.
+    pub fn is_connected(&mut self) -> bool {
+        match self.shutdown_receiver.try_recv() {
+            Ok(None) => true,
+            Ok(Some(())) | Err(oneshot::Canceled) => false,
+        }
+    }
+}