test: test sendall and send do anti-fee-sniping

Author: ishaanam

test/functional/wallet_send.py

@@ -140,7 +140,12 @@ def test_send(self, from_wallet, to_wallet=None, amount=None, data=None,
             return
 
         if locktime:
+            assert_equal(from_wallet.gettransaction(txid=res["txid"], verbose=True)["decoded"]["locktime"], locktime)
             return res
+        else:
+            if add_to_wallet:
+                decoded_tx = from_wallet.gettransaction(txid=res["txid"], verbose=True)["decoded"]
+                assert_greater_than(decoded_tx["locktime"], from_wallet.getblockcount() - 100)
 
         if from_wallet.getwalletinfo()["private_keys_enabled"] and not include_watching:
             assert_equal(res["complete"], True)

test/functional/wallet_sendall.py

@@ -6,6 +6,7 @@
 
 from decimal import Decimal, getcontext
 
+from test_framework.messages import SEQUENCE_FINAL
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -430,6 +431,26 @@ def sendall_does_ancestor_aware_funding(self):
 
         assert_greater_than(higher_parent_feerate_amount, lower_parent_feerate_amount)
 
+    @cleanup
+    def sendall_anti_fee_sniping(self):
+        self.log.info("Testing sendall does anti-fee-sniping when locktime is not specified")
+        self.add_utxos([10,11])
+        tx_from_wallet = self.test_sendall_success(sendall_args = [self.remainder_target])
+
+        assert_greater_than(tx_from_wallet["decoded"]["locktime"], tx_from_wallet["blockheight"] - 100)
+
+        self.log.info("Testing sendall does not do anti-fee-sniping when locktime is specified")
+        self.add_utxos([10,11])
+        txid = self.wallet.sendall(recipients=[self.remainder_target], options={"locktime":0})["txid"]
+        assert_equal(self.wallet.gettransaction(txid=txid, verbose=True)["decoded"]["locktime"], 0)
+
+        self.log.info("Testing sendall does not do anti-fee-sniping when even one of the sequences is final")
+        self.add_utxos([10, 11])
+        utxos = self.wallet.listunspent()
+        utxos[0]["sequence"] = SEQUENCE_FINAL
+        txid = self.wallet.sendall(recipients=[self.remainder_target], inputs=utxos)["txid"]
+        assert_equal(self.wallet.gettransaction(txid=txid, verbose=True)["decoded"]["locktime"], 0)
+
     # This tests needs to be the last one otherwise @cleanup will fail with "Transaction too large" error
     def sendall_fails_with_transaction_too_large(self):
         self.log.info("Test that sendall fails if resulting transaction is too large")
@@ -511,6 +532,9 @@ def run_test(self):
         # Sendall only uses outputs with less than a given number of confirmation when using minconf
         self.sendall_with_maxconf()
 
+        # Sendall discourages fee-sniping when a locktime is not specified
+        self.sendall_anti_fee_sniping()
+
         # Sendall spends unconfirmed change
         self.sendall_spends_unconfirmed_change()