Function TestSendToOutChanLoudOnFirstDrop

pkg/agent/proxy/syncMock/syncMock_test.go:853–908

TestSendToOutChanLoudOnFirstDrop validates the two-message-shape behaviour: the very first drop's Error carries the expanded "recording is now LOSSY" wording, and subsequent sampled emissions (n%1024 == 0) carry the TERSE default. Per Copilot review on PR #4176 the loud signal rides on the existing

(t *testing.T)

// clear actionable line at the moment capture goes lossy, no
// log-level duplication.
func TestSendToOutChanLoudOnFirstDrop(t *testing.T) {
	t.Parallel()

	ch := make(chan *models.Mock, 1)
	mgr := &SyncMockManager{
		buffer: make([]*models.Mock, 0, defaultMockBufferCapacity),
	}
	mgr.SetOutputChannel(ch)

	core, logs := observer.New(zap.ErrorLevel)
	mgr.SetLogger(zap.New(core))

	// Fill the slot so the next send hits the drop branch.
	ch <- &models.Mock{}

	mgr.sendToOutChan(&models.Mock{Spec: models.MockSpec{ReqTimestampMock: time.Now()}})

	if got := mgr.DropCount(); got != 1 {
		t.Fatalf("expected dropCount=1, got %d", got)
	}
	if logs.Len() != 1 {
		t.Fatalf("expected exactly one Error log on first drop, got %d", logs.Len())
	}
	first := logs.All()[0]
	if first.Level != zap.ErrorLevel {
		t.Fatalf("expected Error level, got %v", first.Level)
	}
	// The first-drop message must carry the operator-actionable
	// "LOSSY" wording — the whole point of the expanded n==1
	// message is to surface the actionable cliff signal *the moment*
	// capture stops being whole, so the operator can react before
	// the per-1024 sampler hides hundreds of subsequent drops.
	if !strings.Contains(first.Message, "LOSSY") {
		t.Errorf("first-drop Error missing LOSSY wording: %q", first.Message)
	}

	// Now drive dropCount up to the next sampler milestone (1024)
	// without paying the per-drop wall-clock cost, then walk
	// sendToOutChan once more to fire the n==1024 branch. The
	// emitted message must be the TERSE default — without "LOSSY"
	// — so the sampled telemetry doesn't drown a stuck consumer's
	// goroutine in the long actionable string.
	mgr.dropCount.Store(sendDropSampleRate - 1) // next Add brings n to 1024
	mgr.sendToOutChan(&models.Mock{Spec: models.MockSpec{ReqTimestampMock: time.Now()}})
	if logs.Len() != 2 {
		t.Fatalf("expected a second Error log at n==%d, got total=%d",
			sendDropSampleRate, logs.Len())
	}
	second := logs.All()[1]
	if second.Level != zap.ErrorLevel {
		t.Fatalf("expected Error level on second sampled emission, got %v", second.Level)
	}
	if strings.Contains(second.Message, "LOSSY") {
		t.Errorf("subsequent sampled Error must use terse default; got %q", second.Message)
	}
}

// TestSendToOutChanDropSampling validates the sampling rule: