test: update satoshi_round function

Refactor satoshi_round function to accept different rounding modes.
Updated call site to use the revised `satoshi_round` function.

Co-authored-by: Kate Salazar <52637275+katesalazar@users.noreply.github.com>

test/functional/feature_fee_estimation.py

@@ -4,7 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test fee estimation code."""
 from copy import deepcopy
-from decimal import Decimal
+from decimal import Decimal, ROUND_DOWN
 import os
 import random
 import time
@@ -40,7 +40,7 @@ def small_txpuzzle_randfee(
     # Exponentially distributed from 1-128 * fee_increment
     rand_fee = float(fee_increment) * (1.1892 ** random.randint(0, 28))
     # Total fee ranges from min_fee to min_fee + 127*fee_increment
-    fee = min_fee - fee_increment + satoshi_round(rand_fee)
+    fee = min_fee - fee_increment + satoshi_round(rand_fee, rounding=ROUND_DOWN)
     utxos_to_spend = []
     total_in = Decimal("0.00000000")
     while total_in <= (amount + fee) and len(conflist) > 0:

test/functional/test_framework/util.py

@@ -5,7 +5,7 @@
 """Helpful routines for regression testing."""
 
 from base64 import b64encode
-from decimal import Decimal, ROUND_DOWN
+from decimal import Decimal
 from subprocess import CalledProcessError
 import hashlib
 import inspect
@@ -20,7 +20,9 @@ import time
 from . import coverage
 from .authproxy import AuthServiceProxy, JSONRPCException
 from collections.abc import Callable
-from typing import Optional
+from typing import Optional, Union
+
+SATOSHI_PRECISION = Decimal('0.00000001')
 
 logger = logging.getLogger("TestFramework.utils")
 
@@ -237,8 +239,9 @@ def get_fee(tx_size, feerate_btc_kvb):
     return target_fee_sat / Decimal(1e8) # Return result in  BTC
 
 
-def satoshi_round(amount):
-    return Decimal(amount).quantize(Decimal('0.00000001'), rounding=ROUND_DOWN)
+def satoshi_round(amount: Union[int, float, str], *, rounding: str) -> Decimal:
+    """Rounds a Decimal amount to the nearest satoshi using the specified rounding mode."""
+    return Decimal(amount).quantize(SATOSHI_PRECISION, rounding=rounding)
 
 
 def wait_until_helper_internal(predicate, *, attempts=float('inf'), timeout=float('inf'), lock=None, timeout_factor=1.0):