test: Return the largest utxo in MiniWallet.get_utxo

Author: MarcoFalke

test/functional/rpc_txoutproof.py

@@ -53,7 +53,7 @@ def run_test(self):
         assert_equal(self.nodes[0].verifytxoutproof(self.nodes[0].gettxoutproof([txid1, txid2])), txlist)
         assert_equal(self.nodes[0].verifytxoutproof(self.nodes[0].gettxoutproof([txid1, txid2], blockhash)), txlist)
 
-        txin_spent = miniwallet.get_utxo()  # Get the change from txid2
+        txin_spent = miniwallet.get_utxo(txid=txid2)  # Get the change from txid2
         tx3 = miniwallet.send_self_transfer(from_node=self.nodes[0], utxo_to_spend=txin_spent)
         txid3 = tx3['txid']
         self.generate(self.nodes[0], 1)

test/functional/test_framework/wallet.py

@@ -133,10 +133,9 @@ def get_utxo(self, *, txid: Optional[str]='', mark_as_spent=True):
 
         Args:
         txid: get the first utxo we find from a specific transaction
-
-        Note: Can be used to get the change output immediately after a send_self_transfer
         """
         index = -1  # by default the last utxo
+        self._utxos = sorted(self._utxos, key=lambda k: (k['value'], -k['height']))  # Put the largest utxo last
         if txid:
             utxo = next(filter(lambda utxo: txid == utxo['txid'], self._utxos))
             index = self._utxos.index(utxo)
@@ -172,8 +171,7 @@ def send_to(self, *, from_node, scriptPubKey, amount, fee=1000):
 
     def create_self_transfer(self, *, fee_rate=Decimal("0.003"), from_node, utxo_to_spend=None, mempool_valid=True, locktime=0, sequence=0):
         """Create and return a tx with the specified fee_rate. Fee may be exact or at most one satoshi higher than needed."""
-        self._utxos = sorted(self._utxos, key=lambda k: (k['value'], -k['height']))
-        utxo_to_spend = utxo_to_spend or self._utxos.pop()  # Pick the largest utxo (if none provided) and hope it covers the fee
+        utxo_to_spend = utxo_to_spend or self.get_utxo()
         if self._priv_key is None:
             vsize = Decimal(104)  # anyone-can-spend
         else: