Tests for retry_utils

One can argue about how necessary they are,
but at least I remembered how to do golang.

pkg/util/retryutil/retry_util.go

@@ -5,14 +5,39 @@ import (
 	"time"
 )
 
-// Retry calls ConditionFunc until it returns boolean true, a timeout expires or an error occurs.
+type RetryTicker interface {
+	Stop()
+	Tick()
+}
+
+type Ticker struct {
+	ticker *time.Ticker
+}
+
+func (t *Ticker) Stop() { t.ticker.Stop() }
+
+func (t *Ticker) Tick() { <-t.ticker.C }
+
+// Retry calls ConditionFunc until either:
+// * it returns boolean true
+// * a timeout expires
+// * an error occurs
 func Retry(interval time.Duration, timeout time.Duration, f func() (bool, error)) error {
 	//TODO: make the retry exponential
 	if timeout < interval {
 		return fmt.Errorf("timout(%s) should be greater than interval(%v)", timeout, interval)
 	}
+	tick := &Ticker{time.NewTicker(interval)}
+	return RetryWorker(interval, timeout, f, tick)
+}
+
+func RetryWorker(
+	interval time.Duration,
+	timeout time.Duration,
+	f func() (bool, error),
+	tick RetryTicker) error {
+
 	maxRetries := int(timeout / interval)
-	tick := time.NewTicker(interval)
 	defer tick.Stop()
 
 	for i := 0; ; i++ {
@@ -26,7 +51,7 @@ func Retry(interval time.Duration, timeout time.Duration, f func() (bool, error)
 		if i+1 == maxRetries {
 			break
 		}
-		<-tick.C
+		tick.Tick()
 	}
 	return fmt.Errorf("still failing after %d retries", maxRetries)
 }