test: switch MiniWallet padding unit from weight to vsize

The weight unit is merely a consensus rule detail and is largely
irrelevant for fee-rate calculations and mempool policy rules (e.g. for
package relay and TRUC limits), so there doesn't seem to be any value of
using a granularity that we can't even guarantee to reach exactly
anyway.

Switch to the more natural unit of vsize instead, which simplifies both
the padding implementation and the current tests that take use of this
padding. The rather annoying multiplications by `WITNESS_SCALE_FACTOR`
can then be removed and weird-looking magic numbers like `4004` can be
replaced by numbers that are more connected to actual policy limit
constants from the codebase, e.g. `1001` for exceeding
`TRUC_CHILD_MAX_VSIZE` by one.

6 files changed, 61 insertions, 72 deletions

diff --git a/test/functional/feature_blocksxor.py b/test/functional/feature_blocksxor.py
index 7698a66ec4..9824bf9715 100755
--- a/test/functional/feature_blocksxor.py
+++ b/test/functional/feature_blocksxor.py
@@ -31,7 +31,7 @@ class BlocksXORTest(BitcoinTestFramework):
         node = self.nodes[0]
         wallet = MiniWallet(node)
         for _ in range(5):
-            wallet.send_self_transfer(from_node=node, target_weight=80000)
+            wallet.send_self_transfer(from_node=node, target_vsize=20000)
             self.generate(wallet, 1)
 
         block_files = list(node.blocks_path.glob('blk[0-9][0-9][0-9][0-9][0-9].dat'))
diff --git a/test/functional/feature_framework_miniwallet.py b/test/functional/feature_framework_miniwallet.py
index d1aa24e7cd..f723f7f31e 100755
--- a/test/functional/feature_framework_miniwallet.py
+++ b/test/functional/feature_framework_miniwallet.py
@@ -9,7 +9,7 @@ import string
 from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
-    assert_greater_than_or_equal,
+    assert_equal,
 )
 from test_framework.wallet import (
     MiniWallet,
@@ -22,17 +22,15 @@ class FeatureFrameworkMiniWalletTest(BitcoinTestFramework):
         self.num_nodes = 1
 
     def test_tx_padding(self):
-        """Verify that MiniWallet's transaction padding (`target_weight` parameter)
-           works accurately enough (i.e. at most 3 WUs higher) with all modes."""
+        """Verify that MiniWallet's transaction padding (`target_vsize` parameter)
+           works accurately with all modes."""
         for mode_name, wallet in self.wallets:
             self.log.info(f"Test tx padding with MiniWallet mode {mode_name}...")
             utxo = wallet.get_utxo(mark_as_spent=False)
-            for target_weight in [1000, 2000, 5000, 10000, 20000, 50000, 100000, 200000, 4000000,
-                                  989,  2001, 4337, 13371, 23219, 49153, 102035, 223419, 3999989]:
-                tx = wallet.create_self_transfer(utxo_to_spend=utxo, target_weight=target_weight)["tx"]
-                self.log.debug(f"-> target weight: {target_weight}, actual weight: {tx.get_weight()}")
-                assert_greater_than_or_equal(tx.get_weight(), target_weight)
-                assert_greater_than_or_equal(target_weight + 3, tx.get_weight())
+            for target_vsize in [250, 500, 1250, 2500, 5000, 12500, 25000, 50000, 1000000,
+                                 248, 501, 1085, 3343, 5805, 12289, 25509, 55855,  999998]:
+                tx = wallet.create_self_transfer(utxo_to_spend=utxo, target_vsize=target_vsize)["tx"]
+                assert_equal(tx.get_vsize(), target_vsize)
 
     def test_wallet_tagging(self):
         """Verify that tagged wallet instances are able to send funds."""
diff --git a/test/functional/mempool_limit.py b/test/functional/mempool_limit.py
index 626928a49a..a29c103c3f 100755
--- a/test/functional/mempool_limit.py
+++ b/test/functional/mempool_limit.py
@@ -55,12 +55,12 @@ class MempoolLimitTest(BitcoinTestFramework):
         self.generate(node, 1)
 
         # tx_A needs to be RBF'd, set minfee at set size
-        A_weight = 1000
+        A_vsize = 250
         mempoolmin_feerate = node.getmempoolinfo()["mempoolminfee"]
         tx_A = self.wallet.send_self_transfer(
             from_node=node,
             fee_rate=mempoolmin_feerate,
-            target_weight=A_weight,
+            target_vsize=A_vsize,
             utxo_to_spend=rbf_utxo,
             confirmed_only=True
         )
@@ -68,15 +68,15 @@ class MempoolLimitTest(BitcoinTestFramework):
         # RBF's tx_A, is not yet submitted
         tx_B = self.wallet.create_self_transfer(
             fee=tx_A["fee"] * 4,
-            target_weight=A_weight,
+            target_vsize=A_vsize,
             utxo_to_spend=rbf_utxo,
             confirmed_only=True
         )
 
         # Spends tx_B's output, too big for cpfp carveout (because that would also increase the descendant limit by 1)
-        non_cpfp_carveout_weight = 40001 # EXTRA_DESCENDANT_TX_SIZE_LIMIT + 1
+        non_cpfp_carveout_vsize = 10001  # EXTRA_DESCENDANT_TX_SIZE_LIMIT + 1
         tx_C = self.wallet.create_self_transfer(
-            target_weight=non_cpfp_carveout_weight,
+            target_vsize=non_cpfp_carveout_vsize,
             fee_rate=mempoolmin_feerate,
             utxo_to_spend=tx_B["new_utxo"],
             confirmed_only=True
@@ -103,14 +103,14 @@ class MempoolLimitTest(BitcoinTestFramework):
         # UTXOs to be spent by the ultimate child transaction
         parent_utxos = []
 
-        evicted_weight = 8000
+        evicted_vsize = 2000
         # Mempool transaction which is evicted due to being at the "bottom" of the mempool when the
         # mempool overflows and evicts by descendant score. It's important that the eviction doesn't
         # happen in the middle of package evaluation, as it can invalidate the coins cache.
         mempool_evicted_tx = self.wallet.send_self_transfer(
             from_node=node,
             fee_rate=mempoolmin_feerate,
-            target_weight=evicted_weight,
+            target_vsize=evicted_vsize,
             confirmed_only=True
         )
         # Already in mempool when package is submitted.
@@ -132,14 +132,16 @@ class MempoolLimitTest(BitcoinTestFramework):
 
         # Series of parents that don't need CPFP and are submitted individually. Each one is large and
         # high feerate, which means they should trigger eviction but not be evicted.
-        parent_weight = 100000
+        parent_vsize = 25000
         num_big_parents = 3
-        assert_greater_than(parent_weight * num_big_parents, current_info["maxmempool"] - current_info["bytes"])
+        # Need to be large enough to trigger eviction
+        # (note that the mempool usage of a tx is about three times its vsize)
+        assert_greater_than(parent_vsize * num_big_parents * 3, current_info["maxmempool"] - current_info["bytes"])
         parent_feerate = 100 * mempoolmin_feerate
 
         big_parent_txids = []
         for i in range(num_big_parents):
-            parent = self.wallet.create_self_transfer(fee_rate=parent_feerate, target_weight=parent_weight, confirmed_only=True)
+            parent = self.wallet.create_self_transfer(fee_rate=parent_feerate, target_vsize=parent_vsize, confirmed_only=True)
             parent_utxos.append(parent["new_utxo"])
             package_hex.append(parent["hex"])
             big_parent_txids.append(parent["txid"])
@@ -311,8 +313,9 @@ class MempoolLimitTest(BitcoinTestFramework):
             entry = node.getmempoolentry(txid)
             worst_feerate_btcvb = min(worst_feerate_btcvb, entry["fees"]["descendant"] / entry["descendantsize"])
         # Needs to be large enough to trigger eviction
-        target_weight_each = 200000
-        assert_greater_than(target_weight_each * 2, node.getmempoolinfo()["maxmempool"] - node.getmempoolinfo()["bytes"])
+        # (note that the mempool usage of a tx is about three times its vsize)
+        target_vsize_each = 50000
+        assert_greater_than(target_vsize_each * 2 * 3, node.getmempoolinfo()["maxmempool"] - node.getmempoolinfo()["bytes"])
         # Should be a true CPFP: parent's feerate is just below mempool min feerate
         parent_feerate = mempoolmin_feerate - Decimal("0.000001")  # 0.1 sats/vbyte below min feerate
         # Parent + child is above mempool minimum feerate
@@ -320,8 +323,8 @@ class MempoolLimitTest(BitcoinTestFramework):
         # However, when eviction is triggered, these transactions should be at the bottom.
         # This assertion assumes parent and child are the same size.
         miniwallet.rescan_utxos()
-        tx_parent_just_below = miniwallet.create_self_transfer(fee_rate=parent_feerate, target_weight=target_weight_each)
-        tx_child_just_above = miniwallet.create_self_transfer(utxo_to_spend=tx_parent_just_below["new_utxo"], fee_rate=child_feerate, target_weight=target_weight_each)
+        tx_parent_just_below = miniwallet.create_self_transfer(fee_rate=parent_feerate, target_vsize=target_vsize_each)
+        tx_child_just_above = miniwallet.create_self_transfer(utxo_to_spend=tx_parent_just_below["new_utxo"], fee_rate=child_feerate, target_vsize=target_vsize_each)
         # This package ranks below the lowest descendant package in the mempool
         package_fee = tx_parent_just_below["fee"] + tx_child_just_above["fee"]
         package_vsize = tx_parent_just_below["tx"].get_vsize() + tx_child_just_above["tx"].get_vsize()
diff --git a/test/functional/mempool_package_limits.py b/test/functional/mempool_package_limits.py
index 6e26a684e2..3290ff43c4 100755
--- a/test/functional/mempool_package_limits.py
+++ b/test/functional/mempool_package_limits.py
@@ -4,9 +4,6 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test logic for limiting mempool and package ancestors/descendants."""
 from test_framework.blocktools import COINBASE_MATURITY
-from test_framework.messages import (
-    WITNESS_SCALE_FACTOR,
-)
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -290,19 +287,18 @@ class MempoolPackageLimitsTest(BitcoinTestFramework):
         parent_utxos = []
         target_vsize = 30_000
         high_fee = 10 * target_vsize  # 10 sats/vB
-        target_weight = target_vsize * WITNESS_SCALE_FACTOR
         self.log.info("Check that in-mempool and in-package ancestor size limits are calculated properly in packages")
         # Mempool transactions A and B
         for _ in range(2):
-            bulked_tx = self.wallet.create_self_transfer(target_weight=target_weight)
+            bulked_tx = self.wallet.create_self_transfer(target_vsize=target_vsize)
             self.wallet.sendrawtransaction(from_node=node, tx_hex=bulked_tx["hex"])
             parent_utxos.append(bulked_tx["new_utxo"])
 
         # Package transaction C
-        pc_tx = self.wallet.create_self_transfer_multi(utxos_to_spend=parent_utxos, fee_per_output=high_fee, target_weight=target_weight)
+        pc_tx = self.wallet.create_self_transfer_multi(utxos_to_spend=parent_utxos, fee_per_output=high_fee, target_vsize=target_vsize)
 
         # Package transaction D
-        pd_tx = self.wallet.create_self_transfer(utxo_to_spend=pc_tx["new_utxos"][0], target_weight=target_weight)
+        pd_tx = self.wallet.create_self_transfer(utxo_to_spend=pc_tx["new_utxos"][0], target_vsize=target_vsize)
 
         assert_equal(2, node.getmempoolinfo()["size"])
         return [pc_tx["hex"], pd_tx["hex"]]
@@ -321,20 +317,19 @@ class MempoolPackageLimitsTest(BitcoinTestFramework):
         node = self.nodes[0]
         target_vsize = 21_000
         high_fee = 10 * target_vsize  # 10 sats/vB
-        target_weight = target_vsize * WITNESS_SCALE_FACTOR
         self.log.info("Check that in-mempool and in-package descendant sizes are calculated properly in packages")
         # Top parent in mempool, Ma
-        ma_tx = self.wallet.create_self_transfer_multi(num_outputs=2, fee_per_output=high_fee // 2, target_weight=target_weight)
+        ma_tx = self.wallet.create_self_transfer_multi(num_outputs=2, fee_per_output=high_fee // 2, target_vsize=target_vsize)
         self.wallet.sendrawtransaction(from_node=node, tx_hex=ma_tx["hex"])
 
         package_hex = []
         for j in range(2): # Two legs (left and right)
             # Mempool transaction (Mb and Mc)
-            mempool_tx = self.wallet.create_self_transfer(utxo_to_spend=ma_tx["new_utxos"][j], target_weight=target_weight)
+            mempool_tx = self.wallet.create_self_transfer(utxo_to_spend=ma_tx["new_utxos"][j], target_vsize=target_vsize)
             self.wallet.sendrawtransaction(from_node=node, tx_hex=mempool_tx["hex"])
 
             # Package transaction (Pd and Pe)
-            package_tx = self.wallet.create_self_transfer(utxo_to_spend=mempool_tx["new_utxo"], target_weight=target_weight)
+            package_tx = self.wallet.create_self_transfer(utxo_to_spend=mempool_tx["new_utxo"], target_vsize=target_vsize)
             package_hex.append(package_tx["hex"])
 
         assert_equal(3, node.getmempoolinfo()["size"])
diff --git a/test/functional/mempool_truc.py b/test/functional/mempool_truc.py
index 28f3256ef1..a7b5e83e89 100755
--- a/test/functional/mempool_truc.py
+++ b/test/functional/mempool_truc.py
@@ -6,7 +6,6 @@ from decimal import Decimal
 
 from test_framework.messages import (
     MAX_BIP125_RBF_SEQUENCE,
-    WITNESS_SCALE_FACTOR,
 )
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -55,14 +54,14 @@ class MempoolTRUC(BitcoinTestFramework):
     def test_truc_max_vsize(self):
         node = self.nodes[0]
         self.log.info("Test TRUC-specific maximum transaction vsize")
-        tx_v3_heavy = self.wallet.create_self_transfer(target_weight=(TRUC_MAX_VSIZE + 1) * WITNESS_SCALE_FACTOR, version=3)
+        tx_v3_heavy = self.wallet.create_self_transfer(target_vsize=TRUC_MAX_VSIZE + 1, version=3)
         assert_greater_than_or_equal(tx_v3_heavy["tx"].get_vsize(), TRUC_MAX_VSIZE)
         expected_error_heavy = f"TRUC-violation, version=3 tx {tx_v3_heavy['txid']} (wtxid={tx_v3_heavy['wtxid']}) is too big"
         assert_raises_rpc_error(-26, expected_error_heavy, node.sendrawtransaction, tx_v3_heavy["hex"])
         self.check_mempool([])
 
         # Ensure we are hitting the TRUC-specific limit and not something else
-        tx_v2_heavy = self.wallet.send_self_transfer(from_node=node, target_weight=(TRUC_MAX_VSIZE + 1) * WITNESS_SCALE_FACTOR, version=2)
+        tx_v2_heavy = self.wallet.send_self_transfer(from_node=node, target_vsize=TRUC_MAX_VSIZE + 1, version=2)
         self.check_mempool([tx_v2_heavy["txid"]])
 
     @cleanup(extra_args=["-datacarriersize=1000"])
@@ -73,7 +72,7 @@ class MempoolTRUC(BitcoinTestFramework):
         self.check_mempool([tx_v3_parent_normal["txid"]])
         tx_v3_child_heavy = self.wallet.create_self_transfer(
             utxo_to_spend=tx_v3_parent_normal["new_utxo"],
-            target_weight=4004,
+            target_vsize=1001,
             version=3
         )
         assert_greater_than_or_equal(tx_v3_child_heavy["tx"].get_vsize(), 1000)
@@ -88,7 +87,7 @@ class MempoolTRUC(BitcoinTestFramework):
             from_node=node,
             fee_rate=DEFAULT_FEE,
             utxo_to_spend=tx_v3_parent_normal["new_utxo"],
-            target_weight=3987,
+            target_vsize=997,
             version=3
         )
         assert_greater_than_or_equal(1000, tx_v3_child_almost_heavy["tx"].get_vsize())
@@ -98,7 +97,7 @@ class MempoolTRUC(BitcoinTestFramework):
             from_node=node,
             fee_rate=DEFAULT_FEE * 2,
             utxo_to_spend=tx_v3_parent_normal["new_utxo"],
-            target_weight=3500,
+            target_vsize=875,
             version=3
         )
         assert_greater_than_or_equal(tx_v3_child_almost_heavy["tx"].get_vsize() + tx_v3_child_almost_heavy_rbf["tx"].get_vsize(), 1000)
@@ -199,7 +198,7 @@ class MempoolTRUC(BitcoinTestFramework):
         self.check_mempool([])
         tx_v2_from_v3 = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v3_block["new_utxo"], version=2)
         tx_v3_from_v2 = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v2_block["new_utxo"], version=3)
-        tx_v3_child_large = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v3_block2["new_utxo"], target_weight=5000, version=3)
+        tx_v3_child_large = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=tx_v3_block2["new_utxo"], target_vsize=1250, version=3)
         assert_greater_than(node.getmempoolentry(tx_v3_child_large["txid"])["vsize"], 1000)
         self.check_mempool([tx_v2_from_v3["txid"], tx_v3_from_v2["txid"], tx_v3_child_large["txid"]])
         node.invalidateblock(block[0])
@@ -217,16 +216,16 @@ class MempoolTRUC(BitcoinTestFramework):
         """
         node = self.nodes[0]
         self.log.info("Test that a decreased limitdescendantsize also applies to TRUC child")
-        parent_target_weight = 9990 * WITNESS_SCALE_FACTOR
-        child_target_weight = 500 * WITNESS_SCALE_FACTOR
+        parent_target_vsize = 9990
+        child_target_vsize = 500
         tx_v3_parent_large1 = self.wallet.send_self_transfer(
             from_node=node,
-            target_weight=parent_target_weight,
+            target_vsize=parent_target_vsize,
             version=3
         )
         tx_v3_child_large1 = self.wallet.create_self_transfer(
             utxo_to_spend=tx_v3_parent_large1["new_utxo"],
-            target_weight=child_target_weight,
+            target_vsize=child_target_vsize,
             version=3
         )
 
@@ -244,12 +243,12 @@ class MempoolTRUC(BitcoinTestFramework):
         self.restart_node(0, extra_args=["-limitancestorsize=10", "-datacarriersize=40000"])
         tx_v3_parent_large2 = self.wallet.send_self_transfer(
             from_node=node,
-            target_weight=parent_target_weight,
+            target_vsize=parent_target_vsize,
             version=3
         )
         tx_v3_child_large2 = self.wallet.create_self_transfer(
             utxo_to_spend=tx_v3_parent_large2["new_utxo"],
-            target_weight=child_target_weight,
+            target_vsize=child_target_vsize,
             version=3
         )
 
@@ -267,12 +266,12 @@ class MempoolTRUC(BitcoinTestFramework):
         node = self.nodes[0]
         tx_v3_parent_normal = self.wallet.create_self_transfer(
             fee_rate=0,
-            target_weight=4004,
+            target_vsize=1001,
             version=3
         )
         tx_v3_parent_2_normal = self.wallet.create_self_transfer(
             fee_rate=0,
-            target_weight=4004,
+            target_vsize=1001,
             version=3
         )
         tx_v3_child_multiparent = self.wallet.create_self_transfer_multi(
@@ -282,7 +281,7 @@ class MempoolTRUC(BitcoinTestFramework):
         )
         tx_v3_child_heavy = self.wallet.create_self_transfer_multi(
             utxos_to_spend=[tx_v3_parent_normal["new_utxo"]],
-            target_weight=4004,
+            target_vsize=1001,
             fee_per_output=10000,
             version=3
         )
@@ -294,7 +293,7 @@ class MempoolTRUC(BitcoinTestFramework):
 
         self.check_mempool([])
         result = node.submitpackage([tx_v3_parent_normal["hex"], tx_v3_child_heavy["hex"]])
-        # tx_v3_child_heavy is heavy based on weight, not sigops.
+        # tx_v3_child_heavy is heavy based on vsize, not sigops.
         assert_equal(result['package_msg'], f"TRUC-violation, version=3 child tx {tx_v3_child_heavy['txid']} (wtxid={tx_v3_child_heavy['wtxid']}) is too big: {tx_v3_child_heavy['tx'].get_vsize()} > 1000 virtual bytes")
         self.check_mempool([])
 
@@ -416,7 +415,7 @@ class MempoolTRUC(BitcoinTestFramework):
         node = self.nodes[0]
         tx_v3_parent = self.wallet.create_self_transfer(
             fee_rate=0,
-            target_weight=4004,
+            target_vsize=1001,
             version=3
         )
         tx_v2_child = self.wallet.create_self_transfer_multi(
diff --git a/test/functional/test_framework/wallet.py b/test/functional/test_framework/wallet.py
index f3713f297e..1cef714705 100644
--- a/test/functional/test_framework/wallet.py
+++ b/test/functional/test_framework/wallet.py
@@ -7,7 +7,6 @@
 from copy import deepcopy
 from decimal import Decimal
 from enum import Enum
-import math
 from typing import (
     Any,
     Optional,
@@ -35,7 +34,6 @@ from test_framework.messages import (
     CTxOut,
     hash256,
     ser_compact_size,
-    WITNESS_SCALE_FACTOR,
 )
 from test_framework.script import (
     CScript,
@@ -119,20 +117,18 @@ class MiniWallet:
     def _create_utxo(self, *, txid, vout, value, height, coinbase, confirmations):
         return {"txid": txid, "vout": vout, "value": value, "height": height, "coinbase": coinbase, "confirmations": confirmations}
 
-    def _bulk_tx(self, tx, target_weight):
-        """Pad a transaction with extra outputs until it reaches a target weight (or higher).
+    def _bulk_tx(self, tx, target_vsize):
+        """Pad a transaction with extra outputs until it reaches a target vsize.
         returns the tx
         """
         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
+        # determine number of needed padding bytes
+        dummy_vbytes = target_vsize - tx.get_vsize()
         # 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)
-        assert_greater_than_or_equal(target_weight + 3, tx.get_weight())
+        assert_equal(tx.get_vsize(), target_vsize)
 
     def get_balance(self):
         return sum(u['value'] for u in self._utxos)
@@ -309,7 +305,7 @@ class MiniWallet:
         locktime=0,
         sequence=0,
         fee_per_output=1000,
-        target_weight=0,
+        target_vsize=0,
         confirmed_only=False,
     ):
         """
@@ -338,8 +334,8 @@ class MiniWallet:
 
         self.sign_tx(tx)
 
-        if target_weight:
-            self._bulk_tx(tx, target_weight)
+        if target_vsize:
+            self._bulk_tx(tx, target_vsize)
 
         txid = tx.rehash()
         return {
@@ -364,7 +360,7 @@ class MiniWallet:
             fee_rate=Decimal("0.003"),
             fee=Decimal("0"),
             utxo_to_spend=None,
-            target_weight=0,
+            target_vsize=0,
             confirmed_only=False,
             **kwargs,
     ):
@@ -379,20 +375,18 @@ class MiniWallet:
             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)
+        if target_vsize and not fee:  # respect fee_rate if target vsize is passed
+            fee = get_fee(target_vsize, fee_rate)
         send_value = utxo_to_spend["value"] - (fee or (fee_rate * vsize / 1000))
 
         # create tx
         tx = self.create_self_transfer_multi(
             utxos_to_spend=[utxo_to_spend],
             amount_per_output=int(COIN * send_value),
-            target_weight=target_weight,
+            target_vsize=target_vsize,
             **kwargs,
         )
-        if not target_weight:
+        if not target_vsize:
             assert_equal(tx["tx"].get_vsize(), vsize)
         tx["new_utxo"] = tx.pop("new_utxos")[0]