test(client): avoid scheduler-dependent timing assertions

crates/irtt-client/tests/linux_transport.rs

@@ -108,8 +108,11 @@ fn assert_kernel_send_endpoint(event: &ClientEvent, before_send: SystemTime) {
     let selected =
         i128::from(timing.receive_wall_ns.unwrap()) - one_way.client_to_server.unwrap().as_nanos();
     assert!(selected >= ns(before_send));
-    assert!(
-        selected < ns(sent_at.wall),
+    // TX_SOFTWARE may arrive before or after send returns; only equality
+    // identifies the userspace fallback. Receipt remains the upper bound.
+    assert_ne!(
+        selected,
+        ns(sent_at.wall),
         "TX timestamp was not observed; userspace fallback is insufficient"
     );
     assert!(selected <= ns(received_at.wall));

crates/irtt-integration-tests/tests/managed_behavior.rs

@@ -1,6 +1,10 @@
 mod support;
 
-use std::{collections::HashMap, time::Duration};
+use std::{
+    collections::HashMap,
+    future::{poll_fn, Future},
+    time::Duration,
+};
 
 use irtt_client::{managed::*, ClientConfig, ClientEvent};
 use irtt_server::ServerConfig;
@@ -29,48 +33,60 @@ async fn both_pacing_modes_serve_every_target_on_its_negotiated_grid() {
                 ["first", "second"].map(|id| ManagedTargetConfig::new(id, server.addr.to_string()));
             let (task, handle) = ManagedClient::task(config, targets.into()).unwrap();
             let mut events = handle.subscribe().unwrap();
-            let run = tokio::spawn(task);
+            let mut task = Box::pin(task);
             let mut sends: HashMap<TargetInstance, Vec<_>> = HashMap::new();
-            let mut actual_sends = Vec::new();
-            while let Ok(event) = events.recv().await {
-                if let ManagedEvent::Client {
-                    target,
-                    event:
-                        ClientEvent::EchoSent {
-                            scheduled_at,
-                            sent_at,
-                            ..
-                        },
-                } = event
-                {
-                    let scheduled = scheduled_at.expect("managed probes expose their cadence");
-                    assert!(sent_at.mono >= scheduled);
-                    actual_sends.push((target.clone(), sent_at.mono));
-                    let previous = sends.entry(target).or_default();
-                    if let Some(last) = previous.last() {
-                        let elapsed: Duration = scheduled.duration_since(*last);
-                        assert!(!elapsed.is_zero());
-                        assert_eq!(elapsed.as_nanos() % Duration::from_millis(100).as_nanos(), 0);
+            let mut release_batches = Vec::new();
+            let outcome = poll_fn(|cx| {
+                let result = task.as_mut().poll(cx);
+                let mut released = 0;
+                while let Ok(event) = events.try_recv() {
+                    if let ManagedEvent::Client {
+                        target,
+                        event:
+                            ClientEvent::EchoSent {
+                                scheduled_at,
+                                sent_at,
+                                ..
+                            },
+                    } = event
+                    {
+                        let scheduled = scheduled_at.expect("managed probes expose their cadence");
+                        assert!(sent_at.mono >= scheduled);
+                        released += 1;
+                        let previous = sends.entry(target).or_default();
+                        if let Some(last) = previous.last() {
+                            let elapsed: Duration = scheduled.duration_since(*last);
+                            assert!(!elapsed.is_zero());
+                            assert_eq!(
+                                elapsed.as_nanos() % Duration::from_millis(100).as_nanos(),
+                                0
+                            );
+                        }
+                        previous.push(scheduled);
                     }
-                    previous.push(scheduled);
                 }
-            }
-            let outcome = run.await.unwrap();
+                if released > 0 {
+                    release_batches.push(released);
+                }
+                result
+            })
+            .await;
             assert_eq!(outcome.end_reason, ManagedEndReason::TargetsComplete);
             assert_eq!(outcome.successful_target_outcomes, 2);
             assert_eq!(sends.len(), 2);
-            actual_sends.sort_by_key(|(_, at)| *at);
-            let cross_target_gaps = actual_sends.windows(2)
-                .filter(|pair| pair[0].0 != pair[1].0)
-                .map(|pair| pair[1].1.duration_since(pair[0].1)).collect::<Vec<_>>();
-            assert!(cross_target_gaps.len() >= 2);
-            // Allow timer wake jitter while separating the nominal 50 ms
-            // stagger spacing from back-to-back burst sends.
+            // Drive the public Future and observe the events each poll releases.
+            // Burst serves ready targets together; staggered releases one before
+            // yielding to its next gate. Descheduling cannot stretch/compress an
+            // observed wall-time gap into a different pacing classification.
             match pacing {
-                ManagedPacing::Burst => assert!(cross_target_gaps.iter().filter(|gap| **gap < Duration::from_millis(25)).count() >= 2,
-                    "burst must repeatedly send different targets back-to-back: {cross_target_gaps:?}"),
-                ManagedPacing::Staggered => assert!(cross_target_gaps.iter().all(|gap| *gap >= Duration::from_millis(35)),
-                    "staggered must space different targets across the interval: {cross_target_gaps:?}"),
+                ManagedPacing::Burst => assert!(
+                    release_batches.iter().filter(|count| **count == 2).count() >= 2,
+                    "burst must repeatedly release both ready targets: {release_batches:?}"
+                ),
+                ManagedPacing::Staggered => assert!(
+                    release_batches.iter().all(|count| *count == 1),
+                    "staggered must release targets separately: {release_batches:?}"
+                ),
             }
             for target in outcome.recent_target_outcomes.iter() {
                 assert!(sends[&target.target].len() >= 2);