Add benchmark for random string generation utility

staging/src/k8s.io/apimachinery/pkg/util/rand/rand_test.go

@@ -24,6 +24,7 @@ import (
 
 const (
 	maxRangeTestCount = 500
+	testStringLength  = 32
 )
 
 func TestString(t *testing.T) {
@@ -99,3 +100,15 @@ func TestInt63nRange(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkRandomStringGeneration(b *testing.B) {
+	b.ResetTimer()
+	var s string
+	for i := 0; i < b.N; i++ {
+		s = String(testStringLength)
+	}
+	b.StopTimer()
+	if len(s) == 0 {
+		b.Fatal(s)
+	}
+}