test: Fix intermittent error in mempool_reorg

test/functional/mempool_reorg.py

@@ -16,6 +16,12 @@ from test_framework.util import assert_equal, assert_raises_rpc_error
 class MempoolCoinbaseTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
+        self.extra_args = [
+            [
+                '-whitelist=noban@127.0.0.1',  # immediate tx relay
+            ],
+            []
+        ]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
@@ -67,6 +73,10 @@ class MempoolCoinbaseTest(BitcoinTestFramework):
         # Broadcast and mine 103_1:
         spend_103_1_id = self.nodes[0].sendrawtransaction(spend_103_1_raw)
         last_block = self.nodes[0].generate(1)
+        # Sync blocks, so that peer 1 gets the block before timelock_tx
+        # Otherwise, peer 1 would put the timelock_tx in recentRejects
+        self.sync_all()
+
         # Time-locked transaction can now be spent
         timelock_tx_id = self.nodes[0].sendrawtransaction(timelock_tx)