code: func (h Hash) Generate(rand *rand.Rand, size int) reflect.Value {
  	m := rand.Intn(len(h))
  	for i := len(h) - 1; i > m; i-- {
  		h[i] = byte(rand.Uint32())
  	}
  	return reflect.ValueOf(h)
  }
docs: // Generate implements testing/quick.Generator.