Add integration tests for auth and end-to-end proxying (#4)

* Add authentication handshake tests

* Add basic proxy test

* Add mismatched secret failure test

* Add a failure test for invalid addresses

tests/auth_test.rs

@@ -0,0 +1,35 @@
+use anyhow::Result;
+use bore_cli::auth::Authenticator;
+use tokio::io::{self, BufReader};
+
+#[tokio::test]
+async fn auth_handshake() -> Result<()> {
+    let auth = Authenticator::new("some secret string");
+
+    let (client, server) = io::duplex(8); // Ensure correctness with limited capacity.
+    let mut client = BufReader::new(client);
+    let mut server = BufReader::new(server);
+
+    tokio::try_join!(
+        auth.client_handshake(&mut client),
+        auth.server_handshake(&mut server),
+    )?;
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn auth_handshake_fail() {
+    let auth = Authenticator::new("client secret");
+    let auth2 = Authenticator::new("different server secret");
+
+    let (client, server) = io::duplex(8); // Ensure correctness with limited capacity.
+    let mut client = BufReader::new(client);
+    let mut server = BufReader::new(server);
+
+    let result = tokio::try_join!(
+        auth.client_handshake(&mut client),
+        auth2.server_handshake(&mut server),
+    );
+    assert!(result.is_err());
+}