test: add long-running tool resume tests

Author: DaleSeo

crates/rmcp/tests/test_streamable_http_priming.rs

@@ -271,33 +271,35 @@ async fn test_resume_after_request_wise_channel_completed() -> anyhow::Result<()
     assert!(events[1].contains(r#""id":2"#));
 
     // Resume with Last-Event-ID after the channel has completed.
-    // The cached events should be replayed and the stream should end.
+    // The cached events should be replayed.
     let resume_response = client
         .get(format!("http://{addr}/mcp"))
         .header("Accept", "text/event-stream")
         .header("mcp-session-id", session_id.to_string())
         .header("Mcp-Protocol-Version", "2025-06-18")
         .header("last-event-id", "0/0")
-        .timeout(std::time::Duration::from_secs(5))
         .send()
         .await?;
     assert_eq!(resume_response.status(), 200);
 
-    let resume_body = resume_response.text().await?;
-    let resume_events: Vec<&str> = resume_body
-        .split("\n\n")
-        .filter(|e| !e.is_empty())
-        .collect();
-    assert!(
-        !resume_events.is_empty(),
-        "expected replayed events on resume, got empty"
-    );
-
-    // The replayed event should contain the original response
-    let replayed = resume_events[0];
+    // Read incrementally — the resumed stream may stay open as a
+    // standalone fallback, so we read just enough to verify replay.
+    use futures::StreamExt;
+    let mut stream = resume_response.bytes_stream();
+    let mut buf = String::new();
+    let read_result = tokio::time::timeout(Duration::from_secs(10), async {
+        while let Some(Ok(chunk)) = stream.next().await {
+            buf.push_str(&String::from_utf8_lossy(&chunk));
+            if buf.contains(r#""id":2"#) {
+                return true;
+            }
+        }
+        false
+    })
+    .await;
     assert!(
-        replayed.contains(r#""id":2"#),
-        "replayed event should contain the tool response, got: {replayed}"
+        read_result.unwrap_or(false),
+        "expected replayed tool response on resume, got: {buf}"
     );
 
     ct.cancel();