test: simplify tests by using the pre-mined chain

test/functional/mempool_expiry.py

@@ -12,7 +12,6 @@ definable expiry timeout via the '-mempoolexpiry=<n>' command line argument
 
 from datetime import timedelta
 
-from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.messages import DEFAULT_MEMPOOL_EXPIRY_HOURS
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -27,17 +26,11 @@ CUSTOM_MEMPOOL_EXPIRY = 10  # hours
 class MempoolExpiryTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
-        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.generate(self.wallet, 4)
-        self.generate(node, COINBASE_MATURITY)
 
         # Send a parent transaction that will expire.
         parent_txid = self.wallet.send_self_transfer(from_node=node)['txid']
@@ -97,6 +90,8 @@ class MempoolExpiryTest(BitcoinTestFramework):
         assert_equal(half_expiry_time, node.getmempoolentry(independent_txid)['time'])
 
     def run_test(self):
+        self.wallet = MiniWallet(self.nodes[0])
+
         self.log.info('Test default mempool expiry timeout of %d hours.' %
                       DEFAULT_MEMPOOL_EXPIRY_HOURS)
         self.test_transaction_expiry(DEFAULT_MEMPOOL_EXPIRY_HOURS)