test: introduce tx_from_hex helper for tx deserialization

`FromHex` is mostly used for transactions, so we introduce a
shortcut `tx_from_hex` for `FromHex(CTransaction, hex_str)`.

test/functional/test_framework/blocktools.py

@@ -23,12 +23,12 @@ from .messages import (
     CTxIn,
     CTxInWitness,
     CTxOut,
-    FromHex,
     ToHex,
     hash256,
     hex_str_to_bytes,
     ser_uint256,
     sha256,
+    tx_from_hex,
     uint256_from_str,
 )
 from .script import (
@@ -79,7 +79,7 @@ def create_block(hashprev=None, coinbase=None, ntime=None, *, version=None, tmpl
     if txlist:
         for tx in txlist:
             if not hasattr(tx, 'calc_sha256'):
-                tx = FromHex(CTransaction(), tx)
+                tx = tx_from_hex(tx)
             block.vtx.append(tx)
     block.hashMerkleRoot = block.calc_merkle_root()
     block.calc_sha256()
@@ -166,7 +166,7 @@ def create_transaction(node, txid, to_address, *, amount):
         sign for the output that is being spent.
     """
     raw_tx = create_raw_transaction(node, txid, to_address, amount=amount)
-    tx = FromHex(CTransaction(), raw_tx)
+    tx = tx_from_hex(raw_tx)
     return tx
 
 def create_raw_transaction(node, txid, to_address, *, amount):
@@ -248,7 +248,7 @@ def send_to_witness(use_p2wsh, node, utxo, pubkey, encode_p2sh, amount, sign=Tru
         return node.sendrawtransaction(signed["hex"])
     else:
         if (insert_redeem_script):
-            tx = FromHex(CTransaction(), tx_to_witness)
+            tx = tx_from_hex(tx_to_witness)
             tx.vin[0].scriptSig += CScript([hex_str_to_bytes(insert_redeem_script)])
             tx_to_witness = ToHex(tx)
 

test/functional/test_framework/messages.py

@@ -195,10 +195,17 @@ def FromHex(obj, hex_string):
     obj.deserialize(BytesIO(hex_str_to_bytes(hex_string)))
     return obj
 
+
 # Convert a binary-serializable object to hex (eg for submission via RPC)
 def ToHex(obj):
     return obj.serialize().hex()
 
+
+def tx_from_hex(hex_string):
+    """Deserialize from hex string to a transaction object"""
+    return FromHex(CTransaction(), hex_string)
+
+
 # Objects that map to bitcoind objects, which can be serialized/deserialized
 
 

test/functional/test_framework/util.py

@@ -19,7 +19,6 @@ import unittest
 
 from . import coverage
 from .authproxy import AuthServiceProxy, JSONRPCException
-from io import BytesIO
 from typing import Callable, Optional
 
 logger = logging.getLogger("TestFramework.utils")
@@ -528,7 +527,7 @@ def gen_return_txouts():
 def create_lots_of_big_transactions(node, txouts, utxos, num, fee):
     addr = node.getnewaddress()
     txids = []
-    from .messages import CTransaction
+    from .messages import tx_from_hex
     for _ in range(num):
         t = utxos.pop()
         inputs = [{"txid": t["txid"], "vout": t["vout"]}]
@@ -536,8 +535,7 @@ def create_lots_of_big_transactions(node, txouts, utxos, num, fee):
         change = t['amount'] - fee
         outputs[addr] = satoshi_round(change)
         rawtx = node.createrawtransaction(inputs, outputs)
-        tx = CTransaction()
-        tx.deserialize(BytesIO(hex_str_to_bytes(rawtx)))
+        tx = tx_from_hex(rawtx)
         for txout in txouts:
             tx.vout.append(txout)
         newtx = tx.serialize().hex()