diff --git a/tests/remote_helper_tests.rs b/tests/remote_helper_tests.rs
new file mode 100644
index 0000000..4686a24
--- /dev/null
+++ b/tests/remote_helper_tests.rs
@@ -0,0 +1,56 @@
+//! Drives the remote helper binary the way git does: protocol on stdin/stdout.
+
+use std::process::Stdio;
+
+use tokio::io::AsyncWriteExt;
+
+/// Runs the helper with `commands` on stdin, returning (exit_ok, stdout, stderr).
+async fn run_helper(url: &str, pds_url: &str, commands: &str) -> (bool, String, String) {
+    let mut child = tokio::process::Command::new(env!("CARGO_BIN_EXE_git-remote-pds"))
+        .args(["origin", url])
+        .env("PDS_URL", pds_url)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    child
+        .stdin
+        .as_mut()
+        .unwrap()
+        .write_all(commands.as_bytes())
+        .await
+        .unwrap();
+    child.stdin.take();
+
+    let out = child.wait_with_output().await.unwrap();
+    (
+        out.status.success(),
+        String::from_utf8_lossy(&out.stdout).to_string(),
+        String::from_utf8_lossy(&out.stderr).to_string(),
+    )
+}
+
+/// Port 1 is reserved and nothing listens there — connections fail immediately.
+const DEAD_PDS: &str = "http://127.0.0.1:1";
+
+/// `list` must not answer "this repo has no refs" when it could not reach the PDS.
+///
+/// git treats an empty ref list as an empty repository, so a clone against an
+/// unreachable PDS reports success and leaves an empty repo behind.
+#[tokio::test]
+async fn list_fails_loudly_when_pds_is_unreachable() {
+    let (ok, stdout, stderr) = run_helper("pds://alice.test/some-repo", DEAD_PDS, "list\n").await;
+
+    assert!(
+        !ok,
+        "helper exited 0 despite an unreachable PDS; stdout: {:?}",
+        stdout
+    );
+    assert!(
+        stderr.contains("error"),
+        "expected an error on stderr, got: {:?}",
+        stderr
+    );
+}