Merge bitcoin/bitcoin#30322: test: raise an error in _bulk_tx_ when target_vsize is too low

92787dd test: raise an error when target_vsize is below tx virtual size (ismaelsadeeq)
a8780c9 test: raise an error if output value is <= 0 in `create_self_transfer` (ismaelsadeeq)
f6e8893 test: test that `create_self_transfer_multi` respects `target_vsize` (ismaelsadeeq)

Pull request description:

  This is a simple test PR that does two things:

  1. Raise an exception in `_bulk_tx_` when `target_vsize` is too low, i.e., below the tx vsize.
  2. Addresses some review comments from bitcoin/bitcoin#30162, which are:
     - Raise an error if the output value is less than or equal to zero in `create_self_transfer`.
  This prevents creating transactions with a value of 0 or less.
     - Add a test to verify that `create_self_transfer_multi` also respects the passed `target_vsize`.

ACKs for top commit:
  achow101:
    ACK 92787dd
  theStack:
    ACK 92787dd
  rkrux:
    reACK 92787dd
  glozow:
    ACK 92787dd

Tree-SHA512: 1f2767f2cf715ed65074c5fff347eec160b142685777d833d5e872cfef364d3dc1916b52ee442e99c7b9a8d514ff62bc67a9899d8854f65a4b93ac3ae300d18e

Author: achow101

test/functional/feature_framework_miniwallet.py

@@ -29,8 +29,11 @@ def test_tx_padding(self):
             utxo = wallet.get_utxo(mark_as_spent=False)
             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)
+                tx = wallet.create_self_transfer(utxo_to_spend=utxo, target_vsize=target_vsize)
+                assert_equal(tx['tx'].get_vsize(), target_vsize)
+                child_tx = wallet.create_self_transfer_multi(utxos_to_spend=[tx["new_utxo"]], target_vsize=target_vsize)
+                assert_equal(child_tx['tx'].get_vsize(), target_vsize)
+
 
     def test_wallet_tagging(self):
         """Verify that tagged wallet instances are able to send funds."""

test/functional/test_framework/wallet.py

@@ -121,6 +121,9 @@ def _bulk_tx(self, tx, target_vsize):
         """Pad a transaction with extra outputs until it reaches a target vsize.
         returns the tx
         """
+        if target_vsize < tx.get_vsize():
+            raise RuntimeError(f"target_vsize {target_vsize} is less than transaction virtual size {tx.get_vsize()}")
+
         tx.vout.append(CTxOut(nValue=0, scriptPubKey=CScript([OP_RETURN])))
         # determine number of needed padding bytes
         dummy_vbytes = target_vsize - tx.get_vsize()
@@ -378,7 +381,8 @@ def create_self_transfer(
         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))
-
+        if send_value <= 0:
+            raise RuntimeError(f"UTXO value {utxo_to_spend['value']} is too small to cover fees {(fee or (fee_rate * vsize / 1000))}")
         # create tx
         tx = self.create_self_transfer_multi(
             utxos_to_spend=[utxo_to_spend],