refactor: extract MockSocket to cfg(any(test, fuzz)) module

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/src/util.rs

@@ -7,27 +7,23 @@ pub fn verify_descriptor(desc: &[u8]) {
     assert_eq!(offset, desc.len());
 }
 
-#[cfg(test)]
-pub(crate) mod tests {
+#[cfg(any(test, feature = "fuzz"))]
+pub mod mock {
     use std::{
         io::*,
-        net::SocketAddr,
         pin::Pin,
         sync::{Arc, Mutex},
         task::{Context, Poll},
     };
-    use tokio::{
-        io::{AsyncRead, AsyncWrite, ReadBuf},
-        net::{TcpListener, TcpStream},
-    };
+    use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 
-    pub(crate) struct MockSocket {
+    pub struct MockSocket {
         pub input: Cursor<Vec<u8>>,
         pub output: Arc<Mutex<Vec<u8>>>,
     }
 
     impl MockSocket {
-        pub(crate) fn new(input: Vec<u8>) -> Self {
+        pub fn new(input: Vec<u8>) -> Self {
             Self {
                 input: Cursor::new(input),
                 output: Arc::new(Mutex::new(vec![])),
@@ -35,7 +31,7 @@ pub(crate) mod tests {
         }
 
         /// Get a clone of the output buffer handle for reading after the socket is consumed.
-        pub(crate) fn output_handle(&self) -> Arc<Mutex<Vec<u8>>> {
+        pub fn output_handle(&self) -> Arc<Mutex<Vec<u8>>> {
             self.output.clone()
         }
     }
@@ -51,7 +47,6 @@ pub(crate) mod tests {
         }
     }
 
-    #[cfg(test)]
     impl AsyncWrite for MockSocket {
         fn poll_write(
             self: Pin<&mut Self>,
@@ -70,6 +65,13 @@ pub(crate) mod tests {
             Poll::Ready(Ok(()))
         }
     }
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    pub(crate) use super::mock::MockSocket;
+    use std::net::SocketAddr;
+    use tokio::net::{TcpListener, TcpStream};
 
     pub(crate) async fn get_free_address() -> SocketAddr {
         let stream = TcpListener::bind("127.0.0.1:0").await.unwrap();