test: run mempool_expiry.py even with wallet disabled

Test coverage is also extended in this commit to:
Ensure that another transaction in the mempool is not evicted
when other transactions expire. Note: this other transaction does
not have any ancestors in the mempool that expired. Otherwise it
would be evicted from the mempool, and we already test this case.

Author: mjdietzx

test/functional/mempool_expiry.py

@@ -16,8 +16,8 @@
 from test_framework.util import (
     assert_equal,
     assert_raises_rpc_error,
-    find_vout_for_address,
 )
+from test_framework.wallet import MiniWallet
 
 DEFAULT_MEMPOOL_EXPIRY = 336  # hours
 CUSTOM_MEMPOOL_EXPIRY = 10  # hours
@@ -26,44 +26,50 @@
 class MempoolExpiryTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
-
-    def skip_test_if_missing_module(self):
-        self.skip_if_no_wallet()
+        self.setup_clean_chain = True
 
     def test_transaction_expiry(self, timeout):
         """Tests that a transaction expires after the expiry timeout and its
         children are removed as well."""
         node = self.nodes[0]
+        self.wallet = MiniWallet(node)
+
+        # Add enough mature utxos to the wallet so that all txs spend confirmed coins.
+        self.wallet.generate(4)
+        node.generate(100)
 
         # Send a parent transaction that will expire.
-        parent_address = node.getnewaddress()
-        parent_txid = node.sendtoaddress(parent_address, 1.0)
+        parent_txid = self.wallet.send_self_transfer(from_node=node)['txid']
+        parent_utxo = self.wallet.get_utxo(txid=parent_txid)
+        independent_utxo = self.wallet.get_utxo()
+
+        # Ensure the transactions we send to trigger the mempool check spend utxos that are independent of
+        # the transactions being tested for expiration.
+        trigger_utxo1 = self.wallet.get_utxo()
+        trigger_utxo2 = self.wallet.get_utxo()
 
         # Set the mocktime to the arrival time of the parent transaction.
         entry_time = node.getmempoolentry(parent_txid)['time']
         node.setmocktime(entry_time)
 
-        # Create child transaction spending the parent transaction
-        vout = find_vout_for_address(node, parent_txid, parent_address)
-        inputs = [{'txid': parent_txid, 'vout': vout}]
-        outputs = {node.getnewaddress(): 0.99}
-        child_raw = node.createrawtransaction(inputs, outputs)
-        child_signed = node.signrawtransactionwithwallet(child_raw)['hex']
-
-        # Let half of the timeout elapse and broadcast the child transaction.
+        # Let half of the timeout elapse and broadcast the child transaction spending the parent transaction.
         half_expiry_time = entry_time + int(60 * 60 * timeout/2)
         node.setmocktime(half_expiry_time)
-        child_txid = node.sendrawtransaction(child_signed)
+        child_txid = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=parent_utxo)['txid']
+        assert_equal(parent_txid, node.getmempoolentry(child_txid)['depends'][0])
         self.log.info('Broadcast child transaction after {} hours.'.format(
             timedelta(seconds=(half_expiry_time-entry_time))))
 
+        # Broadcast another (independent) transaction.
+        independent_txid = self.wallet.send_self_transfer(from_node=node, utxo_to_spend=independent_utxo)['txid']
+
         # Let most of the timeout elapse and check that the parent tx is still
         # in the mempool.
         nearly_expiry_time = entry_time + 60 * 60 * timeout - 5
         node.setmocktime(nearly_expiry_time)
-        # Expiry of mempool transactions is only checked when a new transaction
-        # is added to the to the mempool.
-        node.sendtoaddress(node.getnewaddress(), 1.0)
+        # Broadcast a transaction as the expiry of transactions in the mempool is only checked
+        # when a new transaction is added to the mempool.
+        self.wallet.send_self_transfer(from_node=node, utxo_to_spend=trigger_utxo1)
         self.log.info('Test parent tx not expired after {} hours.'.format(
             timedelta(seconds=(nearly_expiry_time-entry_time))))
         assert_equal(entry_time, node.getmempoolentry(parent_txid)['time'])
@@ -72,9 +78,8 @@ def test_transaction_expiry(self, timeout):
         # has passed.
         expiry_time = entry_time + 60 * 60 * timeout + 5
         node.setmocktime(expiry_time)
-        # Expiry of mempool transactions is only checked when a new transaction
-        # is added to the to the mempool.
-        node.sendtoaddress(node.getnewaddress(), 1.0)
+        # Again, broadcast a transaction so the expiry of transactions in the mempool is checked.
+        self.wallet.send_self_transfer(from_node=node, utxo_to_spend=trigger_utxo2)
         self.log.info('Test parent tx expiry after {} hours.'.format(
             timedelta(seconds=(expiry_time-entry_time))))
         assert_raises_rpc_error(-5, 'Transaction not in mempool',
@@ -85,6 +90,11 @@ def test_transaction_expiry(self, timeout):
         assert_raises_rpc_error(-5, 'Transaction not in mempool',
                                 node.getmempoolentry, child_txid)
 
+        # Check that the independent tx is still in the mempool.
+        self.log.info('Test the independent tx not expired after {} hours.'.format(
+            timedelta(seconds=(expiry_time-half_expiry_time))))
+        assert_equal(half_expiry_time, node.getmempoolentry(independent_txid)['time'])
+
     def run_test(self):
         self.log.info('Test default mempool expiry timeout of %d hours.' %
                       DEFAULT_MEMPOOL_EXPIRY)