new_contents: #!/usr/bin/env python3
  # Copyright (c) 2018 The Bitcoin Core developers
  # Distributed under the MIT software license, see the accompanying
  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  """Test wallet group functionality."""
  
  from test_framework.test_framework import BitcoinTestFramework
  from test_framework.messages import CTransaction, FromHex, ToHex
  from test_framework.util import (
      assert_equal,
  )
  
  
  def assert_approx(v, vexp, vspan=0.00001):
      if v < vexp - vspan:
          raise AssertionError("{} < [{}..{}]".format(
              str(v), str(vexp - vspan), str(vexp + vspan)))
      if v > vexp + vspan:
          raise AssertionError("{} > [{}..{}]".format(
              str(v), str(vexp - vspan), str(vexp + vspan)))
  
  
  class WalletGroupTest(BitcoinTestFramework):
      def set_test_params(self):
          self.setup_clean_chain = True
          self.num_nodes = 3
          self.extra_args = [[], [], ['-avoidpartialspends']]
  
      def run_test(self):
          # Mine some coins
          self.nodes[0].generate(110)
  
          # Get some addresses from the two nodes
          addr1 = [self.nodes[1].getnewaddress() for i in range(3)]
          addr2 = [self.nodes[2].getnewaddress() for i in range(3)]
          addrs = addr1 + addr2
  
          # Send 1 + 0.5 coin to each address
          [self.nodes[0].sendtoaddress(addr, 1.0) for addr in addrs]
          [self.nodes[0].sendtoaddress(addr, 0.5) for addr in addrs]
  
          self.nodes[0].generate(1)
          self.sync_all()
  
          # For each node, send 0.2 coins back to 0;
          # - node[1] should pick one 0.5 UTXO and leave the rest
          # - node[2] should pick one (1.0 + 0.5) UTXO group corresponding to a
          #   given address, and leave the rest
          txid1 = self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), 0.2)
          tx1 = self.nodes[1].getrawtransaction(txid1, True)
          # txid1 should have 1 input and 2 outputs
          assert_equal(1, len(tx1["vin"]))
          assert_equal(2, len(tx1["vout"]))
          # one output should be 0.2, the other should be ~0.3
          v = [vout["value"] for vout in tx1["vout"]]
          v.sort()
          assert_approx(v[0], 0.2)
          assert_approx(v[1], 0.3, 0.0001)
  
          txid2 = self.nodes[2].sendtoaddress(self.nodes[0].getnewaddress(), 0.2)
          tx2 = self.nodes[2].getrawtransaction(txid2, True)
          # txid2 should have 2 inputs and 2 outputs
          assert_equal(2, len(tx2["vin"]))
          assert_equal(2, len(tx2["vout"]))
          # one output should be 0.2, the other should be ~1.3
          v = [vout["value"] for vout in tx2["vout"]]
          v.sort()
          assert_approx(v[0], 0.2)
          assert_approx(v[1], 1.3, 0.0001)
  
          # Empty out node2's wallet
          self.nodes[2].sendtoaddress(address=self.nodes[0].getnewaddress(
          ), amount=self.nodes[2].getbalance(), subtractfeefromamount=True)
          self.sync_all()
          self.nodes[0].generate(1)
  
          # Fill node2's wallet with 10000 outputs corresponding to the same
          # scriptPubKey
          for i in range(5):
              raw_tx = self.nodes[0].createrawtransaction(
                  [{"txid": "0"*64, "vout": 0}], [{addr2[0]: 0.05}])
              tx = FromHex(CTransaction(), raw_tx)
              tx.vin = []
              tx.vout = [tx.vout[0]] * 2000
              funded_tx = self.nodes[0].fundrawtransaction(ToHex(tx))
              signed_tx = self.nodes[0].signrawtransactionwithwallet(
                  funded_tx['hex'])
              self.nodes[0].sendrawtransaction(signed_tx['hex'])
              self.nodes[0].generate(1)
  
          self.sync_all()
  
          # Check that we can create a transaction that only requires ~100 of our
          # utxos, without pulling in all outputs and creating a transaction that
          # is way too big.
          assert self.nodes[2].sendtoaddress(address=addr2[0], amount=5)
  
  
  if __name__ == '__main__':
      WalletGroupTest().main()
  
subject: Add basic testing for wallet groups