test(serve): stabilize test_reload_yaml_error flake (status==0 → retry)

rivet-cli/tests/serve_integration.rs

@@ -795,38 +795,54 @@ fn test_csp_header_present() {
 
 // ── STPA-Sec Section 12.4: Dashboard Reload Failure (H-16, SC-18) ─────────
 
+/// POST /reload and parse the HTTP status from the response. Retries
+/// once on `status == 0` — the same transient-connection-drop flake
+/// class `fetch_page_with_retry` handles for GETs, observed under
+/// CI runner load even though the server's health probe has already
+/// passed. Used by the reload-flow tests.
+fn post_reload_status(port: u16) -> u16 {
+    fn once(port: u16) -> u16 {
+        use std::io::{Read, Write};
+        let Ok(mut stream) = std::net::TcpStream::connect(format!("127.0.0.1:{port}")) else {
+            return 0;
+        };
+        let _ = stream.set_read_timeout(Some(Duration::from_secs(30)));
+        let request = format!(
+            "POST /reload HTTP/1.1\r\n\
+             Host: 127.0.0.1:{port}\r\n\
+             HX-Request: true\r\n\
+             Content-Length: 0\r\n\
+             Connection: close\r\n\r\n"
+        );
+        if stream.write_all(request.as_bytes()).is_err() {
+            return 0;
+        }
+        let mut response = Vec::new();
+        let _ = stream.read_to_end(&mut response);
+        let response = String::from_utf8_lossy(&response).to_string();
+        response
+            .lines()
+            .next()
+            .and_then(|l| l.split_whitespace().nth(1))
+            .and_then(|s| s.parse::<u16>().ok())
+            .unwrap_or(0)
+    }
+    let first = once(port);
+    if first != 0 {
+        return first;
+    }
+    std::thread::sleep(Duration::from_millis(200));
+    once(port)
+}
+
 // rivet: verifies SC-18, UCA-D-4
 #[test]
 fn test_reload_yaml_error_returns_error_response() {
     // When a reload is triggered on our valid project, the server must return
     // a success response (200 or redirect) and not crash.
     let (mut child, port) = start_server();
 
-    use std::io::{Read, Write};
-    let mut stream = std::net::TcpStream::connect(format!("127.0.0.1:{port}")).expect("connect");
-    stream
-        .set_read_timeout(Some(std::time::Duration::from_secs(30)))
-        .ok();
-
-    let request = format!(
-        "POST /reload HTTP/1.1\r\n\
-         Host: 127.0.0.1:{port}\r\n\
-         HX-Request: true\r\n\
-         Content-Length: 0\r\n\
-         Connection: close\r\n\r\n"
-    );
-    stream.write_all(request.as_bytes()).expect("write reload");
-
-    let mut response = Vec::new();
-    stream.read_to_end(&mut response).ok();
-    let response = String::from_utf8_lossy(&response).to_string();
-
-    let status = response
-        .lines()
-        .next()
-        .and_then(|l| l.split_whitespace().nth(1))
-        .and_then(|s| s.parse::<u16>().ok())
-        .unwrap_or(0);
+    let status = post_reload_status(port);
 
     assert!(
         status == 200 || (300..400).contains(&status),