default:
			case <-C:
				return
			}
		}
		t.Errorf("missing tick")
	}
	assertLen := func() {
		t.Helper()
		if synctimerchan {
			if n := len(C); n != 0 {
				t.Errorf("synctimer has len(C) = %d, want 0 (always)", n)
			}
			return
		}
		var n int
		if n = len(C); n == 1 {
			return
		}
		for range tries {
			Sleep(sched)
			if n = len(C); n == 1 {
				return