it('should encode vout index', () => {
  expect(HexEncoder.encodeVoutIndex(0)).toStrictEqual('00000000')
  expect(HexEncoder.encodeVoutIndex(1)).toStrictEqual('00000001')
  expect(HexEncoder.encodeVoutIndex(255)).toStrictEqual('000000ff')
  expect(HexEncoder.encodeVoutIndex(256)).toStrictEqual('00000100')