text: #!/usr/bin/python3
  
  # Copyright (c) 2017 Pieter Wuille
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
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  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  # THE SOFTWARE.
  
  
  """Reference tests for segwit adresses"""
  
  import binascii
  import unittest
  from bitcoinaddress import segwit_addr
  
  
  def segwit_scriptpubkey(witver, witprog):
      """Construct a Segwit scriptPubKey for a given witness program."""
      return bytes([witver + 0x50 if witver else 0, len(witprog)] + witprog)
  
  VALID_CHECKSUM = [
      "A12UEL5L",
      "an83characterlonghumanreadablepartthatcontainsthenumber1andtheexcludedcharactersbio1tt5tgs",
      "abcdef1qpzry9x8gf2tvdw0s3jn54khce6mua7lmqqqxw",
      "11qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqc8247j",
      "split1checkupstagehandshakeupstreamerranterredcaperred2y9e3w"
  ]
  
  INVALID_CHECKSUM = [
      " 1nwldj5",
      "\x7F" + "1axkwrx",
      "an84characterslonghumanreadablepartthatcontainsthenumber1andtheexcludedcharactersbio1569pvx",
      "pzry9x0s0muk",
      "1pzry9x0s0muk",
      "x1b4n0q5v",
      "li1dgmt3",
      "de1lg7wt\xff"
      ]
  
  VALID_ADDRESS = [
      ["BC1QW508D6QEJXTDG4Y5R3ZARVARY0C5XW7KV8F3T4", "0014751e76e8199196d454941c45d1b3a323f1433bd6"],
      ["tb1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3q0sl5k7",
       "00201863143c14c5166804bd19203356da136c985678cd4d27a1b8c6329604903262"],
      ["bc1pw508d6qejxtdg4y5r3zarvary0c5xw7kw508d6qejxtdg4y5r3zarvary0c5xw7k7grplx",
       "5128751e76e8199196d454941c45d1b3a323f1433bd6751e76e8199196d454941c45d1b3a323f1433bd6"],
      ["BC1SW50QA3JX3S", "6002751e"],
      ["bc1zw508d6qejxtdg4y5r3zarvaryvg6kdaj", "5210751e76e8199196d454941c45d1b3a323"],
      ["tb1qqqqqp399et2xygdj5xreqhjjvcmzhxw4aywxecjdzew6hylgvsesrxh6hy",
       "0020000000c4a5cad46221b2a187905e5266362b99d5e91c6ce24d165dab93e86433"]
  ]
  
  INVALID_ADDRESS = [
      "tc1qw508d6qejxtdg4y5r3zarvary0c5xw7kg3g4ty",
      "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8f3t5",
      "BC13W508D6QEJXTDG4Y5R3ZARVARY0C5XW7KN40WF2",
      "bc1rw5uspcuh",
      "bc10w508d6qejxtdg4y5r3zarvary0c5xw7kw508d6qejxtdg4y5r3zarvary0c5xw7kw5rljs90",
      "BC1QR508D6QEJXTDG4Y5R3ZARVARYV98GJ9P",
      "tb1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3q0sL5k7",
      "bc1zw508d6qejxtdg4y5r3zarvaryvqyzf3du",
      "tb1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3pjxtptv",
      "bc1gmk9yu"
  ]
  
  INVALID_ADDRESS_ENC = [
      ("BC", 0, 20),
      ("bc", 0, 21),
      ("bc", 17, 32),
      ("bc", 1, 1),
      ("bc", 16, 41),
  ]
  
  class TestSegwitAddress(unittest.TestCase):
      """Unit test class for segwit addressess."""
  
      def test_valid_checksum(self):
          """Test checksum creation and validation."""
          for test in VALID_CHECKSUM:
              hrp, _ = segwit_addr.bech32_decode(test)
              self.assertIsNotNone(hrp)
              pos = test.rfind('1')
              test = test[:pos+1] + chr(ord(test[pos + 1]) ^ 1) + test[pos+2:]
              hrp, _ = segwit_addr.bech32_decode(test)
              self.assertIsNone(hrp)
  
      def test_invalid_checksum(self):
          """Test validation of invalid checksums."""
          for test in INVALID_CHECKSUM:
              hrp, _ = segwit_addr.bech32_decode(test)
              self.assertIsNone(hrp)
  
      def test_valid_address(self):
          """Test whether valid addresses decode to the correct output."""
          for (address, hexscript) in VALID_ADDRESS:
              hrp = "bc"
              witver, witprog = segwit_addr.decode(hrp, address)
              if witver is None:
                  hrp = "tb"
                  witver, witprog = segwit_addr.decode(hrp, address)
              self.assertIsNotNone(witver)
              scriptpubkey = segwit_scriptpubkey(witver, witprog)
              self.assertEqual(scriptpubkey, binascii.unhexlify(hexscript))
              addr = segwit_addr.encode(hrp, witver, witprog)
              self.assertEqual(address.lower(), addr)
  
      def test_invalid_address(self):
          """Test whether invalid addresses fail to decode."""
          for test in INVALID_ADDRESS:
              witver, _ = segwit_addr.decode("bc", test)
              self.assertIsNone(witver)
              witver, _ = segwit_addr.decode("tb", test)
              self.assertIsNone(witver)
  
      def test_invalid_address_enc(self):
          """Test whether address encoding fails on invalid input."""
          for hrp, version, length in INVALID_ADDRESS_ENC:
              code = segwit_addr.encode(hrp, version, [0] * length)
              self.assertIsNone(code)
  
  if __name__ == "__main__":
      unittest.main()