b := make([]byte, 1)
	maxCap := cap(b)
	nGrow := 0
	const N = 1e6
	for i := 0; i < N; i++ {
		b = Insert(b, len(b)-1, 0)
		if cap(b) > maxCap {
			maxCap = cap(b)
			nGrow++
		}
	}
	want := int(math.Log(N) / math.Log(1.25)) // 1.25 == growth rate for large slices
	if nGrow > want {
		t.Errorf("too many grows. got:%d want:%d", nGrow, want)
	}
}