Cover the loss window, rate window, error taxonomy and formatters with tests

loss_test.go

@@ -0,0 +1,91 @@
+package main
+
+import "testing"
+
+func newWindow() *lossWindow {
+	w := newLossWindows(1)
+	return &w[0]
+}
+
+func TestLossWindowContiguousLosesNothing(t *testing.T) {
+	w := newWindow()
+	for seq := uint64(0); seq < lossSlots+1000; seq++ {
+		w.observe(seq)
+	}
+	if got := w.lost.Load(); got != 0 {
+		t.Errorf("lost = %d, want 0", got)
+	}
+	if got := w.late.Load(); got != 0 {
+		t.Errorf("late = %d, want 0", got)
+	}
+}
+
+func TestLossWindowCountsGapOnceEvicted(t *testing.T) {
+	w := newWindow()
+	for seq := uint64(0); seq < lossSlots+1000; seq++ {
+		if seq == 100 {
+			continue
+		}
+		w.observe(seq)
+	}
+	if got := w.lost.Load(); got != 1 {
+		t.Errorf("lost = %d, want 1", got)
+	}
+}
+
+// Arriving out of order inside the window is not loss: a sequence is only
+// judged once it falls out the far end.
+func TestLossWindowOutOfOrderIsNotLoss(t *testing.T) {
+	w := newWindow()
+	for seq := uint64(99); ; seq-- {
+		w.observe(seq)
+		if seq == 0 {
+			break
+		}
+	}
+	for seq := uint64(100); seq < lossSlots+1000; seq++ {
+		w.observe(seq)
+	}
+	if got := w.lost.Load(); got != 0 {
+		t.Errorf("lost = %d, want 0", got)
+	}
+}
+
+// The other branch of evict: a jump past a whole window writes off everything
+// the window held plus the sequences that never landed in it at all.
+func TestLossWindowJumpBeyondWindow(t *testing.T) {
+	w := newWindow()
+	w.observe(0)
+	w.observe(200000)
+
+	// Everything below the new base except the one sequence that was seen.
+	want := uint64(200000 - lossSlots + 1 - 1)
+	if got := w.lost.Load(); got != want {
+		t.Errorf("lost = %d, want %d", got, want)
+	}
+	if got := w.late.Load(); got != 0 {
+		t.Errorf("late = %d, want 0", got)
+	}
+}
+
+func TestLossWindowBelowBaseIsLate(t *testing.T) {
+	w := newWindow()
+	w.observe(100000)
+	w.observe(1000)
+	if got := w.late.Load(); got != 1 {
+		t.Errorf("late = %d, want 1", got)
+	}
+	if got := w.lost.Load(); got != 0 {
+		t.Errorf("lost = %d, want 0", got)
+	}
+}
+
+// The first sequence seen starts the window half a span below it, so frames
+// another worker is still holding land inside rather than arriving late.
+func TestLossWindowStartsHalfAWindowBack(t *testing.T) {
+	w := newWindow()
+	w.observe(100000)
+	if w.base != 100000-lossSlots/2 {
+		t.Errorf("base = %d, want %d", w.base, 100000-lossSlots/2)
+	}
+}