Update test_framework/wallet.py file

Author: janus

test/functional/test_framework/wallet.py

@@ -7,6 +7,7 @@
 from copy import deepcopy
 from decimal import Decimal
 from enum import Enum
+import math
 from typing import (
     Any,
     Optional,
@@ -33,10 +34,13 @@
     CTxInWitness,
     CTxOut,
     hash256,
+    ser_compact_size,
+    WITNESS_SCALE_FACTOR,
 )
 from test_framework.script import (
     CScript,
     LEAF_VERSION_TAPSCRIPT,
+    OP_1,
     OP_NOP,
     OP_RETURN,
     OP_TRUE,
@@ -52,9 +56,8 @@
 from test_framework.util import (
     assert_equal,
     assert_greater_than_or_equal,
+    get_fee,
 )
-from enum import Enum
-from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.wallet_util import generate_keypair
 
 DEFAULT_FEE = Decimal("0.0001")
@@ -109,7 +112,7 @@ def __init__(self, test_node, *, mode=MiniWalletMode.ADDRESS_OP_TRUE, tag_name=N
 
         # When the pre-mined test framework chain is used, it contains coinbase
         # outputs to the MiniWallet's default address in blocks 76-100
-        # (see method BGLTestFramework._initialize_chain())
+        # (see method BitcoinTestFramework._initialize_chain())
         # The MiniWallet needs to rescan_utxos() in order to account
         # for those mature UTXOs, so that all txs spend confirmed coins
         self.rescan_utxos()
@@ -121,13 +124,16 @@ def _bulk_tx(self, tx, target_weight):
         """Pad a transaction with extra outputs until it reaches a target weight (or higher).
         returns the tx
         """
-        tx.vout.append(CTxOut(nValue=0, scriptPubKey=CScript([OP_RETURN, b'a'])))
+        tx.vout.append(CTxOut(nValue=0, scriptPubKey=CScript([OP_RETURN])))
+        # determine number of needed padding bytes by converting weight difference to vbytes
         dummy_vbytes = (target_weight - tx.get_weight() + 3) // 4
-        tx.vout[-1].scriptPubKey = CScript([OP_RETURN, b'a' * dummy_vbytes])
-        # Lower bound should always be off by at most 3
+        # compensate for the increase of the compact-size encoded script length
+        # (note that the length encoding of the unpadded output script needs one byte)
+        dummy_vbytes -= len(ser_compact_size(dummy_vbytes)) - 1
+        tx.vout[-1].scriptPubKey = CScript([OP_RETURN] + [OP_1] * dummy_vbytes)
+        # Actual weight should be at most 3 higher than target weight
         assert_greater_than_or_equal(tx.get_weight(), target_weight)
-        # Higher bound should always be off by at most 3 + 12 weight (for encoding the length)
-        assert_greater_than_or_equal(target_weight + 15, tx.get_weight())
+        assert_greater_than_or_equal(target_weight + 3, tx.get_weight())
 
     def get_balance(self):
         return sum(u['value'] for u in self._utxos)
@@ -369,6 +375,10 @@ def create_self_transfer(
             vsize = Decimal(168)  # P2PK (73 bytes scriptSig + 35 bytes scriptPubKey + 60 bytes other)
         else:
             assert False
+        if target_weight and not fee:  # respect fee_rate if target weight is passed
+            # the actual weight might be off by 3 WUs, so calculate based on that (see self._bulk_tx)
+            max_actual_weight = target_weight + 3
+            fee = get_fee(math.ceil(max_actual_weight / WITNESS_SCALE_FACTOR), fee_rate)
         send_value = utxo_to_spend["value"] - (fee or (fee_rate * vsize / 1000))
 
         # create tx