go func() {
		var buf bytes.Buffer
		io.Copy(&buf, r)
		resultCh <- buf.String()
	}()

	f()
	w.Close()

	return <-resultCh, nil
}

func Test_rudimentaryErrorBackoff_OnError_ParallelSleep(t *testing.T) {
	r := &rudimentaryErrorBackoff{
		minPeriod: time.Second,
	}

	start := make(chan struct{})
	var wg sync.WaitGroup
	for i := 0; i < 30; i++ {
		wg.Add(1)