t.Fatal("SafeWaitGroup released group too soon")
		default:
		}
		wg2.Done()
	}
	for i := 0; i != n; i++ {
		<-exited // Will block if barrier fails to unlock someone.
	}
}

func TestWaitGroupAddFail(t *testing.T) {
	wg := &SafeWaitGroup{}
	wg.Add(1)
	wg.Done()
	wg.Wait()
	if err := wg.Add(1); err == nil {
		t.Errorf("Should return error when add positive after Wait")
	}