Adjust test connection to treat the half-open state more realistically

When a network connection is lost without being explicitly closed by the
other end, writes to that connection will error, but reads will just wait
indefinitely.

This allows the tests to exercise our heartbeat logic.

crates/client/src/test.rs

@@ -6,6 +6,7 @@ use anyhow::{anyhow, Result};
 use futures::{future::BoxFuture, stream::BoxStream, Future, StreamExt};
 use gpui::{executor, ModelHandle, TestAppContext};
 use parking_lot::Mutex;
+use postage::barrier;
 use rpc::{proto, ConnectionId, Peer, Receipt, TypedEnvelope};
 use std::{fmt, rc::Rc, sync::Arc};
 
@@ -22,6 +23,7 @@ struct FakeServerState {
     connection_id: Option<ConnectionId>,
     forbid_connections: bool,
     auth_count: usize,
+    connection_killer: Option<barrier::Sender>,
     access_token: usize,
 }
 
@@ -74,13 +76,15 @@ impl FakeServer {
                             Err(EstablishConnectionError::Unauthorized)?
                         }
 
-                        let (client_conn, server_conn, _) = Connection::in_memory(cx.background());
+                        let (client_conn, server_conn, kill) =
+                            Connection::in_memory(cx.background());
                         let (connection_id, io, incoming) =
                             peer.add_test_connection(server_conn, cx.background()).await;
                         cx.background().spawn(io).detach();
                         let mut state = state.lock();
                         state.connection_id = Some(connection_id);
                         state.incoming = Some(incoming);
+                        state.connection_killer = Some(kill);
                         Ok(client_conn)
                     })
                 }