test(gateway): observe qualification batch pacing

gateway/qualification_contract_test.go

@@ -100,6 +100,15 @@ func TestQualificationApolloFixturePacesSourceShapedVideo(t *testing.T) {
 	fixture := &qualificationApolloFixture{video: sender, failures: make(chan error, 1)}
 	remote := *receiver.LocalAddr().(*net.UDPAddr)
 	fixture.videoRemote.Store(&remote)
+	var batchIndices []int
+	var batchStarts []time.Duration
+	var started time.Time
+	fixture.observeVideoBatch = func(index int, at time.Time) {
+		if len(batchIndices) < 3 {
+			batchIndices = append(batchIndices, index)
+			batchStarts = append(batchStarts, at.Sub(started))
+		}
+	}
 	drained := make(chan struct{})
 	go func() {
 		defer close(drained)
@@ -111,7 +120,7 @@ func TestQualificationApolloFixturePacesSourceShapedVideo(t *testing.T) {
 		}
 	}()
 
-	started := time.Now()
+	started = time.Now()
 	if err := fixture.sendVideo(context.Background(), packets); err != nil {
 		t.Fatal(err)
 	}
@@ -120,9 +129,22 @@ func TestQualificationApolloFixturePacesSourceShapedVideo(t *testing.T) {
 	}
 	elapsed := time.Since(started)
 	wantCarry := qualificationApolloVideoOffset(len(packets), packetsPerMillisecond)
+	if wantCarry != 10416666*time.Nanosecond {
+		t.Fatalf("1000-packet carry = %s, want 10.416666 ms", wantCarry)
+	}
 	if elapsed < wantCarry {
 		t.Fatalf("source fixture sent the next frame after %s, before Apollo pacing carry %s", elapsed, wantCarry)
 	}
+	wantIndices := []int{0, 63, 126}
+	wantStarts := []time.Duration{0, 656250 * time.Nanosecond, 1312500 * time.Nanosecond}
+	if len(batchIndices) != len(wantIndices) {
+		t.Fatalf("observed %d batch starts, want %d", len(batchIndices), len(wantIndices))
+	}
+	for index := range wantIndices {
+		if batchIndices[index] != wantIndices[index] || batchStarts[index] < wantStarts[index] {
+			t.Fatalf("batch starts = indices %v at %v; want indices %v no earlier than %v", batchIndices, batchStarts, wantIndices, wantStarts)
+		}
+	}
 	select {
 	case <-drained:
 	case <-time.After(time.Second):

gateway/qualification_harness_test.go

@@ -414,22 +414,23 @@ func (b *qualificationTracingBackend) session(sessionID string) *nativeApolloSes
 }
 
 type qualificationApolloFixture struct {
-	sessionID   string
-	management  *httptest.Server
-	stream      net.Listener
-	control     *net.UDPConn
-	audio       *net.UDPConn
-	video       *net.UDPConn
-	videoRemote atomic.Pointer[net.UDPAddr]
-	key         atomic.Pointer[[]byte]
-	keyReady    chan []byte
-	failures    chan error
-	closed      atomic.Bool
-	closeOnce   sync.Once
-	sentPackets atomic.Uint64
-	work        protocol.ProviderSessionWork
-	videoPaceMu sync.Mutex
-	videoNext   time.Time
+	sessionID         string
+	management        *httptest.Server
+	stream            net.Listener
+	control           *net.UDPConn
+	audio             *net.UDPConn
+	video             *net.UDPConn
+	videoRemote       atomic.Pointer[net.UDPAddr]
+	key               atomic.Pointer[[]byte]
+	keyReady          chan []byte
+	failures          chan error
+	closed            atomic.Bool
+	closeOnce         sync.Once
+	sentPackets       atomic.Uint64
+	work              protocol.ProviderSessionWork
+	videoPaceMu       sync.Mutex
+	videoNext         time.Time
+	observeVideoBatch func(int, time.Time)
 
 	controlImpairmentMu sync.Mutex
 	controlRTT          time.Duration
@@ -775,11 +776,14 @@ func (f *qualificationApolloFixture) sendVideo(ctx context.Context, packets [][]
 	}
 	framePackets := 0
 	for batchStart := 0; batchStart < len(packets); batchStart += batchSize {
+		batchEnd := min(batchStart+batchSize, len(packets))
 		due := frameStart.Add(qualificationApolloVideoOffset(framePackets, packetsPerMillisecond))
 		if err := qualificationWaitContext(ctx, due); err != nil {
 			return err
 		}
-		batchEnd := min(batchStart+batchSize, len(packets))
+		if f.observeVideoBatch != nil {
+			f.observeVideoBatch(framePackets, time.Now())
+		}
 		for _, packet := range packets[batchStart:batchEnd] {
 			if len(packet) != len(packets[0]) {
 				return ErrProviderMalformed