Merge bitcoin/bitcoin#28232: test: locked_wallet, skip default fee estimation

5364dd8 test: locked_wallet, skip default fee estimation (furszy)

Pull request description:

  Coming from bitcoin/bitcoin#28139 (comment).

  No test case in this file is meant to exercise fee estimation. All default wallets have a
  custom tx fee set [here](https://github.com/bitcoin/bitcoin/blob/b7138252ace6d21476964774e094ed1143cd7a1c/test/functional/wallet_fundrawtransaction.py#L100). The only one missing is the one created for `locked_wallet`.

ACKs for top commit:
  theStack:
    ACK 5364dd8

Tree-SHA512: 514c02708081d18330d759d10e306cee16c6350de243c68f0973777d2582f5d81968a237393c1f59aba245297e03f3f98d3ae5249a042469d0d016255f568719

Author: fanquake

test/functional/wallet_fundrawtransaction.py

@@ -23,6 +23,7 @@
     assert_raises_rpc_error,
     count_bytes,
     find_vout_for_address,
+    get_fee,
 )
 from test_framework.wallet_util import generate_keypair
 
@@ -570,6 +571,8 @@ def test_locked_wallet(self):
         df_wallet = self.nodes[1].get_wallet_rpc(self.default_wallet_name)
         self.nodes[1].createwallet(wallet_name="locked_wallet", descriptors=self.options.descriptors)
         wallet = self.nodes[1].get_wallet_rpc("locked_wallet")
+        # This test is not meant to exercise fee estimation. Making sure all txs are sent at a consistent fee rate.
+        wallet.settxfee(self.min_relay_tx_fee)
 
         # Add some balance to the wallet (this will be reverted at the end of the test)
         df_wallet.sendall(recipients=[wallet.getnewaddress()])
@@ -599,8 +602,11 @@ def test_locked_wallet(self):
 
         # Choose input
         inputs = wallet.listunspent()
-        # Deduce fee to produce a changeless transaction
-        value = inputs[0]["amount"] - Decimal("0.00002200")
+
+        # Deduce exact fee to produce a changeless transaction
+        tx_size = 110  # Total tx size: 110 vbytes, p2wpkh -> p2wpkh. Input 68 vbytes + rest of tx is 42 vbytes.
+        value = inputs[0]["amount"] - get_fee(tx_size, self.min_relay_tx_fee)
+
         outputs = {self.nodes[0].getnewaddress():value}
         rawtx = wallet.createrawtransaction(inputs, outputs)
         # fund a transaction that does not require a new key for the change output