PLT-3753 Added Segment analytics (#3972)

vendor/github.com/segmentio/backo-go/backo_test.go

@@ -0,0 +1,77 @@
+package backo
+
+import (
+	"fmt"
+	"math"
+	"testing"
+	"time"
+
+	"github.com/bmizerany/assert"
+)
+
+// Tests default backo behaviour.
+func TestDefaults(t *testing.T) {
+	backo := DefaultBacko()
+
+	assert.Equal(t, milliseconds(100), backo.Duration(0))
+	assert.Equal(t, milliseconds(200), backo.Duration(1))
+	assert.Equal(t, milliseconds(400), backo.Duration(2))
+	assert.Equal(t, milliseconds(800), backo.Duration(3))
+}
+
+// Tests backo does not exceed cap.
+func TestCap(t *testing.T) {
+	backo := NewBacko(milliseconds(100), 2, 0, milliseconds(600))
+
+	assert.Equal(t, milliseconds(100), backo.Duration(0))
+	assert.Equal(t, milliseconds(200), backo.Duration(1))
+	assert.Equal(t, milliseconds(400), backo.Duration(2))
+	assert.Equal(t, milliseconds(600), backo.Duration(3))
+}
+
+// Tests that jitter adds randomness.
+func TestJitter(t *testing.T) {
+	defaultBacko := NewBacko(milliseconds(100), 2, 1, milliseconds(10*1000))
+	jitterBacko := NewBacko(milliseconds(100), 2, 1, milliseconds(10*1000))
+
+	// TODO: Check jittered durations are within a range.
+	assert.NotEqual(t, jitterBacko.Duration(0), defaultBacko.Duration(0))
+	assert.NotEqual(t, jitterBacko.Duration(1), defaultBacko.Duration(1))
+	assert.NotEqual(t, jitterBacko.Duration(2), defaultBacko.Duration(2))
+	assert.NotEqual(t, jitterBacko.Duration(3), defaultBacko.Duration(3))
+}
+
+func ExampleBacko_BackoffDefault() {
+	b := DefaultBacko()
+	ticker := b.NewTicker()
+
+	for i := 0; i < 6; i++ {
+		start := time.Now()
+		select {
+		case t := <-ticker.C:
+			fmt.Println(nearest10Millis(t.Sub(start)))
+		}
+	}
+
+	ticker.Stop()
+
+	// Output:
+	// 100
+	// 200
+	// 400
+	// 800
+	// 1600
+	// 3200
+}
+
+func nearest10Millis(d time.Duration) float64 {
+	// Typically d is something like 11 or 21, so do some magic to round the
+	// durations to the nearest 10. We divide d by 10, floor it, and multiply it
+	// by 10 again.
+	return math.Floor(float64(d/time.Millisecond/10) * 10)
+}
+
+// Returns the given milliseconds as time.Duration
+func milliseconds(ms int64) time.Duration {
+	return time.Duration(ms * 1000 * 1000)
+}