test: Test for subscriber to print value changes to stdout

tests/test_simple_opc_ua_subscriber.rs

@@ -0,0 +1,69 @@
+mod common;
+mod helpers;
+
+use common::is_port_bound;
+use common::wait_for_function_to_pass;
+use std::process::Stdio;
+use tokio::io::{AsyncBufReadExt, BufReader};
+use tokio::process::Command as TokioCommand;
+use tokio::time::{timeout, Duration as TokioDuration};
+
+#[tokio::test]
+async fn test_simple_subscriber_receives_data_changes() {
+    // Start the server in the background
+    helpers::opc_ua_publisher_single_linear::run_rapid_clock().await;
+
+    let expected_server_port = 4855;
+    wait_for_function_to_pass(|| is_port_bound(expected_server_port), 5000)
+        .expect("Port was not bound within 5 seconds.");
+
+    let mut client_process = TokioCommand::new("cargo")
+        .arg("run")
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("Failed to start client");
+
+    let client_stdout = client_process
+        .stdout
+        .take()
+        .expect("Failed to capture client stdout");
+    let mut reader = BufReader::new(client_stdout).lines();
+
+    let mut found_ticks_since_launch_changed_times = 0u32;
+    let expected_changed_times = 10;
+
+    let read_task = tokio::spawn(async move {
+        while let Some(line) = reader
+            .next_line()
+            .await
+            .expect("Failed to read line from client")
+        {
+            println!("Subscriber stdout: {}", line);
+            if line.contains("Item \"ns=2;s=ticks_since_launch\", Value = Int32(") {
+                found_ticks_since_launch_changed_times += 1;
+                if found_ticks_since_launch_changed_times == expected_changed_times {
+                    return found_ticks_since_launch_changed_times;
+                }
+            }
+        }
+        found_ticks_since_launch_changed_times
+    });
+
+    let timeout_duration = TokioDuration::from_secs(5);
+    match timeout(timeout_duration, read_task).await {
+        Ok(result) => {
+            found_ticks_since_launch_changed_times = result.expect("Failed to join read task");
+        }
+        Err(_) => {
+            eprintln!("Test timed out");
+        }
+    }
+
+    client_process.kill().await.expect("Failed to kill client");
+
+    assert_eq!(
+        found_ticks_since_launch_changed_times, expected_changed_times,
+        "Client did not output enough value changes in time."
+    );
+}