test: Implement a test verifying the helpers integrity

for helpers/opc_ua_publisher_single_linear

Cargo.toml

@@ -16,3 +16,5 @@ categories = ["command-line-utilities"]
 
 [dev-dependencies]
 opcua = { version = "0.12.0", features = ["server", "console-logging"] }
+socket2 = "0.5.7"
+tokio = "1.38.0"

tests/test_helper_opc_ua_publisher.rs

@@ -0,0 +1,68 @@
+use socket2::{Domain, Socket, Type};
+use std::io;
+use std::net::SocketAddr;
+use std::thread;
+use std::time::{Duration, Instant};
+
+mod helpers;
+
+fn is_port_bound(port: u16) -> bool {
+    let socket = match Socket::new(Domain::IPV4, Type::STREAM, None) {
+        Ok(sock) => sock,
+        Err(_) => return false,
+    };
+
+    // Set SO_REUSEADDR to allow for the server to bind while this function is testing
+    if socket.set_reuse_address(true).is_err() {
+        return false;
+    }
+
+    let addr = SocketAddr::from(([127, 0, 0, 1], port));
+
+    // Attempt to bind the socket
+    match socket.bind(&addr.into()) {
+        Ok(_) => false, // Successfully bound, so port was not bound
+        Err(ref e) if e.kind() == io::ErrorKind::AddrInUse => true, // Port is already bound
+        Err(_) => false, // Other errors are treated as port not bound
+    }
+}
+
+fn wait_for_function_to_pass<F>(function: F, timeout_ms: u64) -> Result<(), io::Error>
+where
+    F: Fn() -> bool,
+{
+    let start_time = Instant::now();
+    let timeout_duration = Duration::from_millis(timeout_ms);
+    let check_interval = Duration::from_millis(100);
+
+    while Instant::now().duration_since(start_time) < timeout_duration {
+        if function() {
+            return Ok(());
+        }
+        thread::sleep(check_interval);
+    }
+
+    Err(io::Error::new(
+        io::ErrorKind::TimedOut,
+        "Expectation fn()==True timed out",
+    ))
+}
+
+#[tokio::test]
+async fn test_simple_server_binds_port() {
+    // Start the server in the background
+    helpers::opc_ua_publisher_single_linear::run_rapid_clock().await;
+
+    let expected_server_port = 4855;
+    let res = wait_for_function_to_pass(|| is_port_bound(expected_server_port), 5000);
+
+    match res {
+        Ok(_) => println!("Port was bound within 5 seconds."),
+        Err(e) => {
+            panic!(
+                "Failed to assert port {} binding within the timeout period: {}",
+                expected_server_port, e
+            );
+        }
+    }
+}