test: strengthen durable behavior coverage after review

crates/irtt-stats/src/ipdv.rs

@@ -199,10 +199,23 @@ mod tests {
             ) {
                 let mut tracker = IpdvTracker::new(Some(limit));
                 for seq in seqs {
-                    tracker.insert(ipdv_sample(seq, i128::from(seq)));
+                    let completed_before = tracker.completed_pairs.clone();
+                    let pairs = tracker.insert(ipdv_sample(seq, i128::from(seq)));
+                    let emitted: HashSet<_> = pairs.iter().map(|pair| pair.current_seq).collect();
+                    prop_assert_eq!(emitted.len(), pairs.len());
+                    prop_assert!(emitted.is_disjoint(&completed_before), "a retained pair must not be emitted twice");
                     prop_assert!(tracker.samples.len() <= limit);
                     prop_assert!(tracker.sample_order.len() <= limit);
                     prop_assert!(tracker.completed_pairs.len() <= limit);
+                    // Eviction must remove stale pair markers as well as samples;
+                    // otherwise retained state can prevent future adjacent pairs.
+                    prop_assert_eq!(tracker.sample_order.len(), tracker.samples.len());
+                    prop_assert_eq!(tracker.sample_order.iter().collect::<HashSet<_>>().len(), tracker.samples.len());
+                    prop_assert!(tracker.sample_order.iter().all(|seq| tracker.samples.contains_key(seq)));
+                    prop_assert!(tracker.completed_pairs.iter().all(|seq| {
+                        tracker.samples.contains_key(seq)
+                            && tracker.samples.contains_key(&seq.wrapping_sub(1))
+                    }), "completed pairs must retain both sequence endpoints");
                 }
             }
 

crates/irtt-stats/tests/ipdv.rs

@@ -0,0 +1,112 @@
+use std::time::{Duration, Instant, UNIX_EPOCH};
+
+use irtt_client::{
+    ClientEvent, ClientTimestamp, PacketMeta, RttSample, ServerTiming, SignedDuration,
+};
+use irtt_stats::{StatsCollector, StatsConfig};
+
+fn reply(
+    base: Instant,
+    seq: u32,
+    send_ms: u64,
+    receive_ms: u64,
+    timing: ServerTiming,
+) -> ClientEvent {
+    let raw = Duration::from_millis(receive_ms - send_ms);
+    ClientEvent::EchoReply {
+        seq,
+        remote: "127.0.0.1:2112".parse().unwrap(),
+        sent_at: ClientTimestamp {
+            mono: base + Duration::from_millis(send_ms),
+            wall: UNIX_EPOCH + Duration::from_millis(200 + u64::from(seq) * 10),
+        },
+        received_at: ClientTimestamp {
+            mono: base + Duration::from_millis(receive_ms),
+            wall: UNIX_EPOCH + Duration::from_millis(240 + u64::from(seq) * 20),
+        },
+        rtt: RttSample {
+            raw,
+            adjusted: None,
+            effective: SignedDuration::from_duration(raw),
+        },
+        server_timing: Some(timing),
+        one_way: None,
+        received_stats: None,
+        bytes: 64,
+        packet_meta: PacketMeta::default(),
+    }
+}
+
+#[test]
+fn directional_ipdv_uses_matching_clock_domains_and_preserves_zero_and_absence() {
+    let first = ServerTiming {
+        receive_mono_ns: Some(100_000_000),
+        send_mono_ns: Some(101_000_000),
+        receive_wall_ns: Some(1_000_000_000),
+        send_wall_ns: Some(1_001_000_000),
+        midpoint_mono_ns: None,
+        midpoint_wall_ns: None,
+        processing: None,
+    };
+    let second = ServerTiming {
+        receive_mono_ns: Some(105_000_000),
+        send_mono_ns: Some(108_000_000),
+        receive_wall_ns: Some(1_020_000_000),
+        send_wall_ns: Some(1_026_000_000),
+        ..first
+    };
+    // Wall and monotonic deltas deliberately disagree: availability alone
+    // cannot prove the formulas or which clock domain wins.
+    let mut wall_only = second;
+    wall_only.receive_mono_ns = None;
+    wall_only.send_mono_ns = None;
+    let mut no_send = wall_only;
+    no_send.receive_wall_ns = None;
+    let mut no_receive = wall_only;
+    no_receive.send_wall_ns = None;
+    let zero = ServerTiming {
+        receive_mono_ns: Some(110_000_000),
+        send_mono_ns: Some(111_000_000),
+        ..second
+    };
+    for (label, current, send_ms, expected_send_ms, expected_receive_ms) in [
+        ("monotonic preferred", second, 30, Some(5), Some(3)),
+        ("wall fallback", wall_only, 30, Some(10), Some(5)),
+        ("missing send endpoint", no_send, 30, None, Some(5)),
+        ("missing receive endpoint", no_receive, 30, Some(10), None),
+        ("reordered client send times", second, 10, Some(15), Some(3)),
+        ("zero variation", zero, 30, Some(0), Some(0)),
+    ] {
+        let base = Instant::now();
+        let mut collector = StatsCollector::new(StatsConfig::finite());
+        assert!(collector
+            .process(&reply(base, 0, 20, 40, first))
+            .ipdv_pairs
+            .is_empty());
+        let update = collector.process(&reply(base, 1, send_ms, 50, current));
+        assert_eq!(update.ipdv_pairs.len(), 1, "{label}");
+        let pair = &update.ipdv_pairs[0];
+        assert_eq!(
+            pair.send_ipdv,
+            expected_send_ms.map(Duration::from_millis),
+            "{label}"
+        );
+        assert_eq!(
+            pair.receive_ipdv,
+            expected_receive_ms.map(Duration::from_millis),
+            "{label}"
+        );
+        let snapshot = collector.snapshot();
+        for (expected, actual) in [
+            (expected_send_ms, snapshot.ipdv.send),
+            (expected_receive_ms, snapshot.ipdv.receive),
+        ] {
+            assert_eq!(actual.count, u64::from(expected.is_some()), "{label}");
+            assert_eq!(
+                actual.total_ns,
+                i128::from(expected.unwrap_or(0)) * 1_000_000,
+                "{label}"
+            );
+        }
+    }
+}

crates/irtt-stats/tests/stats.rs

@@ -319,6 +319,19 @@ fn ipdv_wraparound_sequence_is_adjacent() {
     assert!(wrapped.contributed_sample);
     assert_one_ipdv_pair(&wrapped, u32::MAX, 0, Duration::from_millis(4));
 
+    // The client classifies duplicate datagrams before publishing events;
+    // their accounting must not emit an adjacent pair a second time.
+    for seq in [u32::MAX, 0] {
+        let duplicate = collector.process(&ClientEvent::DuplicateReply {
+            seq,
+            remote: "127.0.0.1:2112".parse().unwrap(),
+            received_at: ts(30),
+            bytes: 64,
+        });
+        assert!(!duplicate.contributed_sample);
+        assert_no_ipdv_pairs(&duplicate);
+    }
+
     let snapshot = collector.snapshot();
     assert_eq!(snapshot.ipdv.round_trip.count, 1);
     assert_eq!(snapshot.ipdv.round_trip.total_ns, 4_000_000);
@@ -355,19 +368,6 @@ fn late_reply_can_complete_ipdv_pair() {
     assert_eq!(snapshot.ipdv.round_trip.total_ns, 10_000_000);
 }
 
-#[test]
-fn update_exposes_directional_ipdv_when_available() {
-    let mut collector = StatsCollector::new(StatsConfig::finite());
-    collector.process(&unadjusted_reply(0, 10));
-    let update = collector.process(&unadjusted_reply(1, 13));
-
-    assert!(update.contributed_sample);
-
-    let pair = assert_one_ipdv_pair(&update, 0, 1, Duration::from_millis(3));
-    assert!(pair.send_ipdv.is_some());
-    assert!(pair.receive_ipdv.is_some());
-}
-
 #[test]
 fn gap_fill_update_exposes_both_completed_ipdv_pairs() {
     let mut collector = StatsCollector::new(StatsConfig::finite());