test: remove `ToHex` helper, use .serialize().hex() instead

17 files changed, 128 insertions, 102 deletions

diff --git a/contrib/signet/miner b/contrib/signet/miner
index 0c3a9c145e..d36813a591 100755
--- a/contrib/signet/miner
+++ b/contrib/signet/miner
@@ -23,7 +23,7 @@ PATH_BASE_TEST_FUNCTIONAL = os.path.abspath(os.path.join(PATH_BASE_CONTRIB_SIGNE
 sys.path.insert(0, PATH_BASE_TEST_FUNCTIONAL)
 
 from test_framework.blocktools import WITNESS_COMMITMENT_HEADER, script_BIP34_coinbase_height # noqa: E402
-from test_framework.messages import CBlock, CBlockHeader, COutPoint, CTransaction, CTxIn, CTxInWitness, CTxOut, FromHex, ToHex, deser_string, hash256, ser_compact_size, ser_string, ser_uint256, tx_from_hex, uint256_from_str # noqa: E402
+from test_framework.messages import CBlock, CBlockHeader, COutPoint, CTransaction, CTxIn, CTxInWitness, CTxOut, FromHex, deser_string, hash256, ser_compact_size, ser_string, ser_uint256, tx_from_hex, uint256_from_str # noqa: E402
 from test_framework.script import CScriptOp # noqa: E402
 
 logging.basicConfig(
@@ -274,7 +274,7 @@ def do_genpsbt(args):
 def do_solvepsbt(args):
     block, signet_solution = do_decode_psbt(sys.stdin.read())
     block = finish_block(block, signet_solution, args.grind_cmd)
-    print(ToHex(block))
+    print(block.serialize().hex())
 
 def nbits_to_target(nbits):
     shift = (nbits >> 24) & 0xff
@@ -503,7 +503,7 @@ def do_generate(args):
         block = finish_block(block, signet_solution, args.grind_cmd)
 
         # submit block
-        r = args.bcli("-stdin", "submitblock", input=ToHex(block).encode('utf8'))
+        r = args.bcli("-stdin", "submitblock", input=block.serialize().hex().encode('utf8'))
 
         # report
         bstr = "block" if is_mine else "backup block"
diff --git a/test/functional/feature_bip68_sequence.py b/test/functional/feature_bip68_sequence.py
index 2b2341fb03..e44ce9b57d 100755
--- a/test/functional/feature_bip68_sequence.py
+++ b/test/functional/feature_bip68_sequence.py
@@ -17,7 +17,6 @@ from test_framework.messages import (
     CTransaction,
     CTxIn,
     CTxOut,
-    ToHex,
     tx_from_hex,
 )
 from test_framework.test_framework import BitcoinTestFramework
@@ -101,7 +100,7 @@ class BIP68Test(BitcoinTestFramework):
         tx1.vin = [CTxIn(COutPoint(int(utxo["txid"], 16), utxo["vout"]), nSequence=sequence_value)]
         tx1.vout = [CTxOut(value, DUMMY_P2WPKH_SCRIPT)]
 
-        tx1_signed = self.nodes[0].signrawtransactionwithwallet(ToHex(tx1))["hex"]
+        tx1_signed = self.nodes[0].signrawtransactionwithwallet(tx1.serialize().hex())["hex"]
         tx1_id = self.nodes[0].sendrawtransaction(tx1_signed)
         tx1_id = int(tx1_id, 16)
 
@@ -114,13 +113,13 @@ class BIP68Test(BitcoinTestFramework):
         tx2.vout = [CTxOut(int(value - self.relayfee * COIN), DUMMY_P2WPKH_SCRIPT)]
         tx2.rehash()
 
-        assert_raises_rpc_error(-26, NOT_FINAL_ERROR, self.nodes[0].sendrawtransaction, ToHex(tx2))
+        assert_raises_rpc_error(-26, NOT_FINAL_ERROR, self.nodes[0].sendrawtransaction, tx2.serialize().hex())
 
         # Setting the version back down to 1 should disable the sequence lock,
         # so this should be accepted.
         tx2.nVersion = 1
 
-        self.nodes[0].sendrawtransaction(ToHex(tx2))
+        self.nodes[0].sendrawtransaction(tx2.serialize().hex())
 
     # Calculate the median time past of a prior block ("confirmations" before
     # the current tip).
@@ -205,9 +204,9 @@ class BIP68Test(BitcoinTestFramework):
                 tx.vin.append(CTxIn(COutPoint(int(utxos[j]["txid"], 16), utxos[j]["vout"]), nSequence=sequence_value))
                 value += utxos[j]["amount"]*COIN
             # Overestimate the size of the tx - signatures should be less than 120 bytes, and leave 50 for the output
-            tx_size = len(ToHex(tx))//2 + 120*num_inputs + 50
+            tx_size = len(tx.serialize().hex())//2 + 120*num_inputs + 50
             tx.vout.append(CTxOut(int(value-self.relayfee*tx_size*COIN/1000), DUMMY_P2WPKH_SCRIPT))
-            rawtx = self.nodes[0].signrawtransactionwithwallet(ToHex(tx))["hex"]
+            rawtx = self.nodes[0].signrawtransactionwithwallet(tx.serialize().hex())["hex"]
 
             if (using_sequence_locks and not should_pass):
                 # This transaction should be rejected
@@ -236,7 +235,7 @@ class BIP68Test(BitcoinTestFramework):
         tx2.nVersion = 2
         tx2.vin = [CTxIn(COutPoint(tx1.sha256, 0), nSequence=0)]
         tx2.vout = [CTxOut(int(tx1.vout[0].nValue - self.relayfee*COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx2_raw = self.nodes[0].signrawtransactionwithwallet(ToHex(tx2))["hex"]
+        tx2_raw = self.nodes[0].signrawtransactionwithwallet(tx2.serialize().hex())["hex"]
         tx2 = tx_from_hex(tx2_raw)
         tx2.rehash()
 
@@ -258,10 +257,10 @@ class BIP68Test(BitcoinTestFramework):
 
             if (orig_tx.hash in node.getrawmempool()):
                 # sendrawtransaction should fail if the tx is in the mempool
-                assert_raises_rpc_error(-26, NOT_FINAL_ERROR, node.sendrawtransaction, ToHex(tx))
+                assert_raises_rpc_error(-26, NOT_FINAL_ERROR, node.sendrawtransaction, tx.serialize().hex())
             else:
                 # sendrawtransaction should succeed if the tx is not in the mempool
-                node.sendrawtransaction(ToHex(tx))
+                node.sendrawtransaction(tx.serialize().hex())
 
             return tx
 
@@ -311,7 +310,7 @@ class BIP68Test(BitcoinTestFramework):
         utxos = self.nodes[0].listunspent()
         tx5.vin.append(CTxIn(COutPoint(int(utxos[0]["txid"], 16), utxos[0]["vout"]), nSequence=1))
         tx5.vout[0].nValue += int(utxos[0]["amount"]*COIN)
-        raw_tx5 = self.nodes[0].signrawtransactionwithwallet(ToHex(tx5))["hex"]
+        raw_tx5 = self.nodes[0].signrawtransactionwithwallet(tx5.serialize().hex())["hex"]
 
         assert_raises_rpc_error(-26, NOT_FINAL_ERROR, self.nodes[0].sendrawtransaction, raw_tx5)
 
@@ -337,7 +336,7 @@ class BIP68Test(BitcoinTestFramework):
             block.rehash()
             block.solve()
             tip = block.sha256
-            assert_equal(None if i == 1 else 'inconclusive', self.nodes[0].submitblock(ToHex(block)))
+            assert_equal(None if i == 1 else 'inconclusive', self.nodes[0].submitblock(block.serialize().hex()))
             tmpl = self.nodes[0].getblocktemplate(NORMAL_GBT_REQUEST_PARAMS)
             tmpl['previousblockhash'] = '%x' % tip
             tmpl['transactions'] = []
@@ -370,11 +369,11 @@ class BIP68Test(BitcoinTestFramework):
         tx2.vout = [CTxOut(int(tx1.vout[0].nValue - self.relayfee*COIN), DUMMY_P2WPKH_SCRIPT)]
 
         # sign tx2
-        tx2_raw = self.nodes[0].signrawtransactionwithwallet(ToHex(tx2))["hex"]
+        tx2_raw = self.nodes[0].signrawtransactionwithwallet(tx2.serialize().hex())["hex"]
         tx2 = tx_from_hex(tx2_raw)
         tx2.rehash()
 
-        self.nodes[0].sendrawtransaction(ToHex(tx2))
+        self.nodes[0].sendrawtransaction(tx2.serialize().hex())
 
         # Now make an invalid spend of tx2 according to BIP68
         sequence_value = 100 # 100 block relative locktime
@@ -385,7 +384,7 @@ class BIP68Test(BitcoinTestFramework):
         tx3.vout = [CTxOut(int(tx2.vout[0].nValue - self.relayfee * COIN), DUMMY_P2WPKH_SCRIPT)]
         tx3.rehash()
 
-        assert_raises_rpc_error(-26, NOT_FINAL_ERROR, self.nodes[0].sendrawtransaction, ToHex(tx3))
+        assert_raises_rpc_error(-26, NOT_FINAL_ERROR, self.nodes[0].sendrawtransaction, tx3.serialize().hex())
 
         # make a block that violates bip68; ensure that the tip updates
         block = create_block(tmpl=self.nodes[0].getblocktemplate(NORMAL_GBT_REQUEST_PARAMS))
@@ -418,7 +417,7 @@ class BIP68Test(BitcoinTestFramework):
         rawtxfund = self.nodes[1].fundrawtransaction(rawtx)['hex']
         tx = tx_from_hex(rawtxfund)
         tx.nVersion = 2
-        tx_signed = self.nodes[1].signrawtransactionwithwallet(ToHex(tx))["hex"]
+        tx_signed = self.nodes[1].signrawtransactionwithwallet(tx.serialize().hex())["hex"]
         self.nodes[1].sendrawtransaction(tx_signed)
 
 if __name__ == '__main__':
diff --git a/test/functional/feature_coinstatsindex.py b/test/functional/feature_coinstatsindex.py
index cf270b25ee..48c6d82c13 100755
--- a/test/functional/feature_coinstatsindex.py
+++ b/test/functional/feature_coinstatsindex.py
@@ -22,7 +22,6 @@ from test_framework.messages import (
     CTransaction,
     CTxIn,
     CTxOut,
-    ToHex,
 )
 from test_framework.script import (
     CScript,
@@ -170,7 +169,7 @@ class CoinStatsIndexTest(BitcoinTestFramework):
         tx2 = CTransaction()
         tx2.vin.append(CTxIn(COutPoint(int(tx1_txid, 16), n), b''))
         tx2.vout.append(CTxOut(int(20.99 * COIN), CScript([OP_RETURN] + [OP_FALSE]*30)))
-        tx2_hex = self.nodes[0].signrawtransactionwithwallet(ToHex(tx2))['hex']
+        tx2_hex = self.nodes[0].signrawtransactionwithwallet(tx2.serialize().hex())['hex']
         self.nodes[0].sendrawtransaction(tx2_hex)
 
         # Include both txs in a block
@@ -207,7 +206,7 @@ class CoinStatsIndexTest(BitcoinTestFramework):
         block_time = self.nodes[0].getblock(tip)['time'] + 1
         block = create_block(int(tip, 16), cb, block_time)
         block.solve()
-        self.nodes[0].submitblock(ToHex(block))
+        self.nodes[0].submitblock(block.serialize().hex())
         self.sync_all()
 
         self.wait_until(lambda: not try_rpc(-32603, "Unable to read UTXO set", index_node.gettxoutsetinfo, 'muhash'))
diff --git a/test/functional/feature_dbcrash.py b/test/functional/feature_dbcrash.py
index 2b56bc78f5..c532300ce2 100755
--- a/test/functional/feature_dbcrash.py
+++ b/test/functional/feature_dbcrash.py
@@ -36,7 +36,6 @@ from test_framework.messages import (
     CTransaction,
     CTxIn,
     CTxOut,
-    ToHex,
 )
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -208,7 +207,7 @@ class ChainstateWriteCrashTest(BitcoinTestFramework):
                 tx.vout.append(CTxOut(output_amount, hex_str_to_bytes(utxo['scriptPubKey'])))
 
             # Sign and send the transaction to get into the mempool
-            tx_signed_hex = node.signrawtransactionwithwallet(ToHex(tx))['hex']
+            tx_signed_hex = node.signrawtransactionwithwallet(tx.serialize().hex())['hex']
             node.sendrawtransaction(tx_signed_hex)
             num_transactions += 1
 
diff --git a/test/functional/feature_fee_estimation.py b/test/functional/feature_fee_estimation.py
index 8f522aee66..8ccdf87ff3 100755
--- a/test/functional/feature_fee_estimation.py
+++ b/test/functional/feature_fee_estimation.py
@@ -6,8 +6,23 @@
 from decimal import Decimal
 import random
 
-from test_framework.messages import CTransaction, CTxIn, CTxOut, COutPoint, ToHex, COIN
-from test_framework.script import CScript, OP_1, OP_DROP, OP_2, OP_HASH160, OP_EQUAL, hash160, OP_TRUE
+from test_framework.messages import (
+    COIN,
+    COutPoint,
+    CTransaction,
+    CTxIn,
+    CTxOut,
+)
+from test_framework.script import (
+    CScript,
+    OP_1,
+    OP_2,
+    OP_DROP,
+    OP_EQUAL,
+    OP_HASH160,
+    OP_TRUE,
+    hash160,
+)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -64,11 +79,11 @@ def small_txpuzzle_randfee(from_node, conflist, unconflist, amount, min_fee, fee
     # the ScriptSig that will satisfy the ScriptPubKey.
     for inp in tx.vin:
         inp.scriptSig = SCRIPT_SIG[inp.prevout.n]
-    txid = from_node.sendrawtransaction(hexstring=ToHex(tx), maxfeerate=0)
+    txid = from_node.sendrawtransaction(hexstring=tx.serialize().hex(), maxfeerate=0)
     unconflist.append({"txid": txid, "vout": 0, "amount": total_in - amount - fee})
     unconflist.append({"txid": txid, "vout": 1, "amount": amount})
 
-    return (ToHex(tx), fee)
+    return (tx.serialize().hex(), fee)
 
 
 def split_inputs(from_node, txins, txouts, initial_split=False):
@@ -91,10 +106,10 @@ def split_inputs(from_node, txins, txouts, initial_split=False):
     # If this is the initial split we actually need to sign the transaction
     # Otherwise we just need to insert the proper ScriptSig
     if (initial_split):
-        completetx = from_node.signrawtransactionwithwallet(ToHex(tx))["hex"]
+        completetx = from_node.signrawtransactionwithwallet(tx.serialize().hex())["hex"]
     else:
         tx.vin[0].scriptSig = SCRIPT_SIG[prevtxout["vout"]]
-        completetx = ToHex(tx)
+        completetx = tx.serialize().hex()
     txid = from_node.sendrawtransaction(hexstring=completetx, maxfeerate=0)
     txouts.append({"txid": txid, "vout": 0, "amount": half_change})
     txouts.append({"txid": txid, "vout": 1, "amount": rem_change})
diff --git a/test/functional/feature_pruning.py b/test/functional/feature_pruning.py
index f09bffe2d4..cedb7b57ca 100755
--- a/test/functional/feature_pruning.py
+++ b/test/functional/feature_pruning.py
@@ -11,8 +11,12 @@ This test takes 30 mins or more (up to 2 hours)
 import os
 
 from test_framework.blocktools import create_coinbase
-from test_framework.messages import CBlock, ToHex
-from test_framework.script import CScript, OP_RETURN, OP_NOP
+from test_framework.messages import CBlock
+from test_framework.script import (
+    CScript,
+    OP_NOP,
+    OP_RETURN,
+)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -62,7 +66,7 @@ def mine_large_blocks(node, n):
         block.solve()
 
         # Submit to the node
-        node.submitblock(ToHex(block))
+        node.submitblock(block.serialize().hex())
 
         previousblockhash = block.sha256
         height += 1
diff --git a/test/functional/feature_rbf.py b/test/functional/feature_rbf.py
index b99b64e16d..e42f8045db 100755
--- a/test/functional/feature_rbf.py
+++ b/test/functional/feature_rbf.py
@@ -7,7 +7,14 @@
 from decimal import Decimal
 
 from test_framework.blocktools import COINBASE_MATURITY
-from test_framework.messages import COIN, COutPoint, CTransaction, CTxIn, CTxOut, BIP125_SEQUENCE_NUMBER
+from test_framework.messages import (
+    BIP125_SEQUENCE_NUMBER,
+    COIN,
+    COutPoint,
+    CTransaction,
+    CTxIn,
+    CTxOut,
+)
 from test_framework.script import CScript, OP_DROP
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal, assert_raises_rpc_error, satoshi_round
@@ -17,10 +24,6 @@ from test_framework.wallet import MiniWallet
 MAX_REPLACEMENT_LIMIT = 100
 
 
-def txToHex(tx):
-    return tx.serialize().hex()
-
-
 def make_utxo(node, amount, confirmed=True, scriptPubKey=DUMMY_P2WPKH_SCRIPT):
     """Create a txout with a given amount and scriptPubKey
 
@@ -44,7 +47,7 @@ def make_utxo(node, amount, confirmed=True, scriptPubKey=DUMMY_P2WPKH_SCRIPT):
     tx2.vout = [CTxOut(amount, scriptPubKey)]
     tx2.rehash()
 
-    signed_tx = node.signrawtransactionwithwallet(txToHex(tx2))
+    signed_tx = node.signrawtransactionwithwallet(tx2.serialize().hex())
 
     txid = node.sendrawtransaction(signed_tx['hex'], 0)
 
@@ -133,7 +136,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1a = CTransaction()
         tx1a.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1a_hex = txToHex(tx1a)
+        tx1a_hex = tx1a.serialize().hex()
         tx1a_txid = self.nodes[0].sendrawtransaction(tx1a_hex, 0)
 
         self.sync_all()
@@ -142,7 +145,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(1 * COIN, DUMMY_2_P2WPKH_SCRIPT)]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
 
         # This will raise an exception due to insufficient fee
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx1b_hex, 0)
@@ -151,7 +154,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(int(0.9 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
         # Works when enabled
         tx1b_txid = self.nodes[0].sendrawtransaction(tx1b_hex, 0)
 
@@ -176,7 +179,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
             tx = CTransaction()
             tx.vin = [CTxIn(prevout, nSequence=0)]
             tx.vout = [CTxOut(remaining_value, CScript([1, OP_DROP] * 15 + [1]))]
-            tx_hex = txToHex(tx)
+            tx_hex = tx.serialize().hex()
             txid = self.nodes[0].sendrawtransaction(tx_hex, 0)
             chain_txids.append(txid)
             prevout = COutPoint(int(txid, 16), 0)
@@ -186,7 +189,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         dbl_tx = CTransaction()
         dbl_tx.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         dbl_tx.vout = [CTxOut(initial_nValue - 30 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        dbl_tx_hex = txToHex(dbl_tx)
+        dbl_tx_hex = dbl_tx.serialize().hex()
 
         # This will raise an exception due to insufficient fee
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, dbl_tx_hex, 0)
@@ -195,7 +198,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         dbl_tx = CTransaction()
         dbl_tx.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         dbl_tx.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        dbl_tx_hex = txToHex(dbl_tx)
+        dbl_tx_hex = dbl_tx.serialize().hex()
         self.nodes[0].sendrawtransaction(dbl_tx_hex, 0)
 
         mempool = self.nodes[0].getrawmempool()
@@ -223,7 +226,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
             tx = CTransaction()
             tx.vin = [CTxIn(prevout, nSequence=0)]
             tx.vout = vout
-            tx_hex = txToHex(tx)
+            tx_hex = tx.serialize().hex()
 
             assert len(tx.serialize()) < 100000
             txid = self.nodes[0].sendrawtransaction(tx_hex, 0)
@@ -248,7 +251,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         dbl_tx = CTransaction()
         dbl_tx.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         dbl_tx.vout = [CTxOut(initial_nValue - fee * n, DUMMY_P2WPKH_SCRIPT)]
-        dbl_tx_hex = txToHex(dbl_tx)
+        dbl_tx_hex = dbl_tx.serialize().hex()
         # This will raise an exception due to insufficient fee
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, dbl_tx_hex, 0)
 
@@ -256,7 +259,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         dbl_tx = CTransaction()
         dbl_tx.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         dbl_tx.vout = [CTxOut(initial_nValue - fee * n - 1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        dbl_tx_hex = txToHex(dbl_tx)
+        dbl_tx_hex = dbl_tx.serialize().hex()
         self.nodes[0].sendrawtransaction(dbl_tx_hex, 0)
 
         mempool = self.nodes[0].getrawmempool()
@@ -276,7 +279,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
             dbl_tx = CTransaction()
             dbl_tx.vin = [CTxIn(tx0_outpoint, nSequence=0)]
             dbl_tx.vout = [CTxOut(initial_nValue - 2 * fee * n, DUMMY_P2WPKH_SCRIPT)]
-            dbl_tx_hex = txToHex(dbl_tx)
+            dbl_tx_hex = dbl_tx.serialize().hex()
             # This will raise an exception
             assert_raises_rpc_error(-26, "too many potential replacements", self.nodes[0].sendrawtransaction, dbl_tx_hex, 0)
 
@@ -291,7 +294,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1a = CTransaction()
         tx1a.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1a_hex = txToHex(tx1a)
+        tx1a_hex = tx1a.serialize().hex()
         self.nodes[0].sendrawtransaction(tx1a_hex, 0)
 
         # Higher fee, but the fee per KB is much lower, so the replacement is
@@ -299,7 +302,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(int(0.001 * COIN), CScript([b'a' * 999000]))]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
 
         # This will raise an exception due to insufficient fee
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx1b_hex, 0)
@@ -312,7 +315,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1a = CTransaction()
         tx1a.vin = [CTxIn(utxo1, nSequence=0)]
         tx1a.vout = [CTxOut(int(1.1 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx1a_hex = txToHex(tx1a)
+        tx1a_hex = tx1a.serialize().hex()
         tx1a_txid = self.nodes[0].sendrawtransaction(tx1a_hex, 0)
 
         tx1a_txid = int(tx1a_txid, 16)
@@ -322,7 +325,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx2.vin = [CTxIn(utxo1, nSequence=0), CTxIn(utxo2, nSequence=0)]
         tx2.vin.append(CTxIn(COutPoint(tx1a_txid, 0), nSequence=0))
         tx2.vout = tx1a.vout
-        tx2_hex = txToHex(tx2)
+        tx2_hex = tx2.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "bad-txns-spends-conflicting-tx", self.nodes[0].sendrawtransaction, tx2_hex, 0)
@@ -331,7 +334,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(COutPoint(tx1a_txid, 0), nSequence=0)]
         tx1b.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
         tx1b_txid = self.nodes[0].sendrawtransaction(tx1b_hex, 0)
         tx1b_txid = int(tx1b_txid, 16)
 
@@ -339,7 +342,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx2.vin = [CTxIn(utxo1, nSequence=0), CTxIn(utxo2, nSequence=0),
                    CTxIn(COutPoint(tx1b_txid, 0))]
         tx2.vout = tx1a.vout
-        tx2_hex = txToHex(tx2)
+        tx2_hex = tx2.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "bad-txns-spends-conflicting-tx", self.nodes[0].sendrawtransaction, tx2_hex, 0)
@@ -352,13 +355,13 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1 = CTransaction()
         tx1.vin = [CTxIn(confirmed_utxo)]
         tx1.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1_hex = txToHex(tx1)
+        tx1_hex = tx1.serialize().hex()
         self.nodes[0].sendrawtransaction(tx1_hex, 0)
 
         tx2 = CTransaction()
         tx2.vin = [CTxIn(confirmed_utxo), CTxIn(unconfirmed_utxo)]
         tx2.vout = tx1.vout
-        tx2_hex = txToHex(tx2)
+        tx2_hex = tx2.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "replacement-adds-unconfirmed", self.nodes[0].sendrawtransaction, tx2_hex, 0)
@@ -381,7 +384,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         splitting_tx = CTransaction()
         splitting_tx.vin = [CTxIn(utxo, nSequence=0)]
         splitting_tx.vout = outputs
-        splitting_tx_hex = txToHex(splitting_tx)
+        splitting_tx_hex = splitting_tx.serialize().hex()
 
         txid = self.nodes[0].sendrawtransaction(splitting_tx_hex, 0)
         txid = int(txid, 16)
@@ -391,7 +394,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
             tx_i = CTransaction()
             tx_i.vin = [CTxIn(COutPoint(txid, i), nSequence=0)]
             tx_i.vout = [CTxOut(split_value - fee, DUMMY_P2WPKH_SCRIPT)]
-            tx_i_hex = txToHex(tx_i)
+            tx_i_hex = tx_i.serialize().hex()
             self.nodes[0].sendrawtransaction(tx_i_hex, 0)
 
         # Now create doublespend of the whole lot; should fail.
@@ -404,7 +407,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         double_tx = CTransaction()
         double_tx.vin = inputs
         double_tx.vout = [CTxOut(double_spend_value, CScript([b'a']))]
-        double_tx_hex = txToHex(double_tx)
+        double_tx_hex = double_tx.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "too many potential replacements", self.nodes[0].sendrawtransaction, double_tx_hex, 0)
@@ -413,7 +416,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         double_tx = CTransaction()
         double_tx.vin = inputs[0:-1]
         double_tx.vout = [CTxOut(double_spend_value, CScript([b'a']))]
-        double_tx_hex = txToHex(double_tx)
+        double_tx_hex = double_tx.serialize().hex()
         self.nodes[0].sendrawtransaction(double_tx_hex, 0)
 
     def test_opt_in(self):
@@ -424,7 +427,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1a = CTransaction()
         tx1a.vin = [CTxIn(tx0_outpoint, nSequence=0xffffffff)]
         tx1a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1a_hex = txToHex(tx1a)
+        tx1a_hex = tx1a.serialize().hex()
         tx1a_txid = self.nodes[0].sendrawtransaction(tx1a_hex, 0)
 
         # This transaction isn't shown as replaceable
@@ -434,7 +437,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(int(0.9 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "txn-mempool-conflict", self.nodes[0].sendrawtransaction, tx1b_hex, 0)
@@ -445,14 +448,14 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx2a = CTransaction()
         tx2a.vin = [CTxIn(tx1_outpoint, nSequence=0xfffffffe)]
         tx2a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx2a_hex = txToHex(tx2a)
+        tx2a_hex = tx2a.serialize().hex()
         tx2a_txid = self.nodes[0].sendrawtransaction(tx2a_hex, 0)
 
         # Still shouldn't be able to double-spend
         tx2b = CTransaction()
         tx2b.vin = [CTxIn(tx1_outpoint, nSequence=0)]
         tx2b.vout = [CTxOut(int(0.9 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx2b_hex = txToHex(tx2b)
+        tx2b_hex = tx2b.serialize().hex()
 
         # This will raise an exception
         assert_raises_rpc_error(-26, "txn-mempool-conflict", self.nodes[0].sendrawtransaction, tx2b_hex, 0)
@@ -468,7 +471,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx3a.vin = [CTxIn(COutPoint(tx1a_txid, 0), nSequence=0xffffffff),
                     CTxIn(COutPoint(tx2a_txid, 0), nSequence=0xfffffffd)]
         tx3a.vout = [CTxOut(int(0.9 * COIN), CScript([b'c'])), CTxOut(int(0.9 * COIN), CScript([b'd']))]
-        tx3a_hex = txToHex(tx3a)
+        tx3a_hex = tx3a.serialize().hex()
 
         tx3a_txid = self.nodes[0].sendrawtransaction(tx3a_hex, 0)
 
@@ -478,12 +481,12 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx3b = CTransaction()
         tx3b.vin = [CTxIn(COutPoint(tx1a_txid, 0), nSequence=0)]
         tx3b.vout = [CTxOut(int(0.5 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx3b_hex = txToHex(tx3b)
+        tx3b_hex = tx3b.serialize().hex()
 
         tx3c = CTransaction()
         tx3c.vin = [CTxIn(COutPoint(tx2a_txid, 0), nSequence=0)]
         tx3c.vout = [CTxOut(int(0.5 * COIN), DUMMY_P2WPKH_SCRIPT)]
-        tx3c_hex = txToHex(tx3c)
+        tx3c_hex = tx3c.serialize().hex()
 
         self.nodes[0].sendrawtransaction(tx3b_hex, 0)
         # If tx3b was accepted, tx3c won't look like a replacement,
@@ -500,14 +503,14 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx1a = CTransaction()
         tx1a.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx1a_hex = txToHex(tx1a)
+        tx1a_hex = tx1a.serialize().hex()
         tx1a_txid = self.nodes[0].sendrawtransaction(tx1a_hex, 0)
 
         # Higher fee, but the actual fee per KB is much lower.
         tx1b = CTransaction()
         tx1b.vin = [CTxIn(tx0_outpoint, nSequence=0)]
         tx1b.vout = [CTxOut(int(0.001 * COIN), CScript([b'a' * 740000]))]
-        tx1b_hex = txToHex(tx1b)
+        tx1b_hex = tx1b.serialize().hex()
 
         # Verify tx1b cannot replace tx1a.
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx1b_hex, 0)
@@ -526,7 +529,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx2a = CTransaction()
         tx2a.vin = [CTxIn(tx1_outpoint, nSequence=0)]
         tx2a.vout = [CTxOut(1 * COIN, DUMMY_P2WPKH_SCRIPT)]
-        tx2a_hex = txToHex(tx2a)
+        tx2a_hex = tx2a.serialize().hex()
         self.nodes[0].sendrawtransaction(tx2a_hex, 0)
 
         # Lower fee, but we'll prioritise it
@@ -534,7 +537,7 @@ class ReplaceByFeeTest(BitcoinTestFramework):
         tx2b.vin = [CTxIn(tx1_outpoint, nSequence=0)]
         tx2b.vout = [CTxOut(int(1.01 * COIN), DUMMY_P2WPKH_SCRIPT)]
         tx2b.rehash()
-        tx2b_hex = txToHex(tx2b)
+        tx2b_hex = tx2b.serialize().hex()
 
         # Verify tx2b cannot replace tx2a.
         assert_raises_rpc_error(-26, "insufficient fee", self.nodes[0].sendrawtransaction, tx2b_hex, 0)
diff --git a/test/functional/feature_segwit.py b/test/functional/feature_segwit.py
index 0f62701305..42910904d7 100755
--- a/test/functional/feature_segwit.py
+++ b/test/functional/feature_segwit.py
@@ -23,7 +23,6 @@ from test_framework.messages import (
     CTransaction,
     CTxIn,
     CTxOut,
-    ToHex,
     sha256,
     tx_from_hex,
 )
@@ -268,7 +267,7 @@ class SegWitTest(BitcoinTestFramework):
         tx = CTransaction()
         tx.vin.append(CTxIn(COutPoint(int(txid1, 16), 0), b''))
         tx.vout.append(CTxOut(int(49.99 * COIN), CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))
-        tx2_hex = self.nodes[0].signrawtransactionwithwallet(ToHex(tx))['hex']
+        tx2_hex = self.nodes[0].signrawtransactionwithwallet(tx.serialize().hex())['hex']
         txid2 = self.nodes[0].sendrawtransaction(tx2_hex)
         tx = tx_from_hex(tx2_hex)
         assert not tx.wit.is_null()
@@ -285,7 +284,7 @@ class SegWitTest(BitcoinTestFramework):
         tx.vin.append(CTxIn(COutPoint(int(txid2, 16), 0), b""))
         tx.vout.append(CTxOut(int(49.95 * COIN), CScript([OP_TRUE, OP_DROP] * 15 + [OP_TRUE])))  # Huge fee
         tx.calc_sha256()
-        txid3 = self.nodes[0].sendrawtransaction(hexstring=ToHex(tx), maxfeerate=0)
+        txid3 = self.nodes[0].sendrawtransaction(hexstring=tx.serialize().hex(), maxfeerate=0)
         assert tx.wit.is_null()
         assert txid3 in self.nodes[0].getrawmempool()
 
diff --git a/test/functional/feature_taproot.py b/test/functional/feature_taproot.py
index fc04853199..99283b69b0 100755
--- a/test/functional/feature_taproot.py
+++ b/test/functional/feature_taproot.py
@@ -19,7 +19,6 @@ from test_framework.messages import (
     CTxIn,
     CTxInWitness,
     CTxOut,
-    ToHex,
 )
 from test_framework.script import (
     ANNEX_TAG,
@@ -1306,7 +1305,7 @@ class TaprootTest(BitcoinTestFramework):
             # Add change
             fund_tx.vout.append(CTxOut(balance - 10000, random.choice(host_spks)))
             # Ask the wallet to sign
-            ss = BytesIO(bytes.fromhex(node.signrawtransactionwithwallet(ToHex(fund_tx))["hex"]))
+            ss = BytesIO(bytes.fromhex(node.signrawtransactionwithwallet(fund_tx.serialize().hex())["hex"]))
             fund_tx.deserialize(ss)
             # Construct UTXOData entries
             fund_tx.rehash()
diff --git a/test/functional/interface_zmq.py b/test/functional/interface_zmq.py
index 0534618d06..15f352d68c 100755
--- a/test/functional/interface_zmq.py
+++ b/test/functional/interface_zmq.py
@@ -5,8 +5,15 @@
 """Test the ZMQ notification interface."""
 import struct
 
-from test_framework.address import ADDRESS_BCRT1_UNSPENDABLE, ADDRESS_BCRT1_P2WSH_OP_TRUE
-from test_framework.blocktools import create_block, create_coinbase, add_witness_commitment
+from test_framework.address import (
+    ADDRESS_BCRT1_P2WSH_OP_TRUE,
+    ADDRESS_BCRT1_UNSPENDABLE,
+)
+from test_framework.blocktools import (
+    add_witness_commitment,
+    create_block,
+    create_coinbase,
+)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.messages import (
     CTransaction,
diff --git a/test/functional/p2p_compactblocks.py b/test/functional/p2p_compactblocks.py
index 3c771df0aa..6b8e2b3050 100755
--- a/test/functional/p2p_compactblocks.py
+++ b/test/functional/p2p_compactblocks.py
@@ -34,7 +34,6 @@ from test_framework.messages import (
     NODE_NETWORK,
     P2PHeaderAndShortIDs,
     PrefilledTransaction,
-    ToHex,
     calculate_shortid,
     msg_block,
     msg_blocktxn,
@@ -62,7 +61,10 @@ from test_framework.script import (
     OP_TRUE,
 )
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, softfork_active
+from test_framework.util import (
+    assert_equal,
+    softfork_active,
+)
 
 # TestP2PConn: A peer we use to send messages to bitcoind, and store responses.
 class TestP2PConn(P2PInterface):
@@ -715,9 +717,9 @@ class CompactBlocksTest(BitcoinTestFramework):
 
         [l.clear_block_announcement() for l in listeners]
 
-        # ToHex() won't serialize with witness, but this block has no witnesses
-        # anyway. TODO: repeat this test with witness tx's to a segwit node.
-        node.submitblock(ToHex(block))
+        # serialize without witness (this block has no witnesses anyway).
+        # TODO: repeat this test with witness tx's to a segwit node.
+        node.submitblock(block.serialize().hex())
 
         for l in listeners:
             l.wait_until(lambda: "cmpctblock" in l.last_message, timeout=30)
diff --git a/test/functional/rpc_rawtransaction.py b/test/functional/rpc_rawtransaction.py
index b3d5771534..db57368eae 100755
--- a/test/functional/rpc_rawtransaction.py
+++ b/test/functional/rpc_rawtransaction.py
@@ -18,7 +18,6 @@ from decimal import Decimal
 from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.messages import (
     CTransaction,
-    ToHex,
     tx_from_hex,
 )
 from test_framework.test_framework import BitcoinTestFramework
@@ -451,14 +450,14 @@ class RawTransactionsTest(BitcoinTestFramework):
         # As transaction version is unsigned, this should convert to its unsigned equivalent.
         tx = CTransaction()
         tx.nVersion = -0x80000000
-        rawtx = ToHex(tx)
+        rawtx = tx.serialize().hex()
         decrawtx = self.nodes[0].decoderawtransaction(rawtx)
         assert_equal(decrawtx['version'], 0x80000000)
 
         # Test the maximum transaction version number that fits in a signed 32-bit integer.
         tx = CTransaction()
         tx.nVersion = 0x7fffffff
-        rawtx = ToHex(tx)
+        rawtx = tx.serialize().hex()
         decrawtx = self.nodes[0].decoderawtransaction(rawtx)
         assert_equal(decrawtx['version'], 0x7fffffff)
 
diff --git a/test/functional/rpc_txoutproof.py b/test/functional/rpc_txoutproof.py
index bf96b6353c..9afeeaff10 100755
--- a/test/functional/rpc_txoutproof.py
+++ b/test/functional/rpc_txoutproof.py
@@ -5,9 +5,15 @@
 """Test gettxoutproof and verifytxoutproof RPCs."""
 
 from test_framework.blocktools import COINBASE_MATURITY
-from test_framework.messages import CMerkleBlock, FromHex, ToHex
+from test_framework.messages import (
+    CMerkleBlock,
+    FromHex,
+)
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+)
 from test_framework.wallet import MiniWallet
 
 
@@ -91,7 +97,7 @@ class MerkleBlockTest(BitcoinTestFramework):
         tweaked_proof = FromHex(CMerkleBlock(), proof)
 
         # Make sure that our serialization/deserialization is working
-        assert txid1 in self.nodes[0].verifytxoutproof(ToHex(tweaked_proof))
+        assert txid1 in self.nodes[0].verifytxoutproof(tweaked_proof.serialize().hex())
 
         # Check to see if we can go up the merkle tree and pass this off as a
         # single-transaction block
@@ -100,7 +106,7 @@ class MerkleBlockTest(BitcoinTestFramework):
         tweaked_proof.txn.vBits = [True] + [False]*7
 
         for n in self.nodes:
-            assert not n.verifytxoutproof(ToHex(tweaked_proof))
+            assert not n.verifytxoutproof(tweaked_proof.serialize().hex())
 
         # TODO: try more variants, eg transactions at different depths, and
         # verify that the proofs are invalid
diff --git a/test/functional/test_framework/blocktools.py b/test/functional/test_framework/blocktools.py
index 0019b7a426..fa943cb716 100644
--- a/test/functional/test_framework/blocktools.py
+++ b/test/functional/test_framework/blocktools.py
@@ -23,7 +23,6 @@ from .messages import (
     CTxIn,
     CTxInWitness,
     CTxOut,
-    ToHex,
     hash256,
     hex_str_to_bytes,
     ser_uint256,
@@ -250,7 +249,7 @@ def send_to_witness(use_p2wsh, node, utxo, pubkey, encode_p2sh, amount, sign=Tru
         if (insert_redeem_script):
             tx = tx_from_hex(tx_to_witness)
             tx.vin[0].scriptSig += CScript([hex_str_to_bytes(insert_redeem_script)])
-            tx_to_witness = ToHex(tx)
+            tx_to_witness = tx.serialize().hex()
 
     return node.sendrawtransaction(tx_to_witness)
 
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index 43c80fa7a8..f43c1eb10f 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -196,11 +196,6 @@ def FromHex(obj, 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)
diff --git a/test/functional/wallet_groups.py b/test/functional/wallet_groups.py
index 1b52ddcba5..d9d135a986 100755
--- a/test/functional/wallet_groups.py
+++ b/test/functional/wallet_groups.py
@@ -7,7 +7,6 @@
 from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.messages import (
-    ToHex,
     tx_from_hex,
 )
 from test_framework.util import (
@@ -160,7 +159,7 @@ class WalletGroupTest(BitcoinTestFramework):
             tx = tx_from_hex(raw_tx)
             tx.vin = []
             tx.vout = [tx.vout[0]] * 2000
-            funded_tx = self.nodes[0].fundrawtransaction(ToHex(tx))
+            funded_tx = self.nodes[0].fundrawtransaction(tx.serialize().hex())
             signed_tx = self.nodes[0].signrawtransactionwithwallet(funded_tx['hex'])
             self.nodes[0].sendrawtransaction(signed_tx['hex'])
             self.nodes[0].generate(1)
diff --git a/test/functional/wallet_resendwallettransactions.py b/test/functional/wallet_resendwallettransactions.py
index 78d88f8aa5..37dee219e7 100755
--- a/test/functional/wallet_resendwallettransactions.py
+++ b/test/functional/wallet_resendwallettransactions.py
@@ -5,8 +5,10 @@
 """Test that the wallet resends transactions periodically."""
 import time
 
-from test_framework.blocktools import create_block, create_coinbase
-from test_framework.messages import ToHex
+from test_framework.blocktools import (
+    create_block,
+    create_coinbase,
+)
 from test_framework.p2p import P2PTxInvStore
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal
@@ -48,7 +50,7 @@ class ResendWalletTransactionsTest(BitcoinTestFramework):
         block = create_block(int(node.getbestblockhash(), 16), create_coinbase(node.getblockcount() + 1), block_time)
         block.rehash()
         block.solve()
-        node.submitblock(ToHex(block))
+        node.submitblock(block.serialize().hex())
 
         # Set correct m_best_block_time, which is used in ResendWalletTransactions
         node.syncwithvalidationinterfacequeue()