Merge bitcoin/bitcoin#29394: test, assumeutxo: Add test to ensure failure when mempool not empty

8d20602 test, assumeutxo: Add test to ensure failure when mempool not empty (Hernan Marino)

Pull request description:

  Add a test to ensure that loadtxoutset fails when the node's mempool is not empty, as suggested by maflcko  here: bitcoin/bitcoin#27596 (comment)

ACKs for top commit:
  maflcko:
    re-ACK 8d20602
  BrandonOdiwuor:
    ACK 8d20602

Tree-SHA512: 97c9668c0f38897934bf0d326515d898d4e682ff219deba9d751b35125b5cf33d51c9df116a74117ecf0394f28995a3d0cae1266b1e5acb4365ff4f309ce3f6c

Author: fanquake

test/functional/feature_assumeutxo.py

@@ -60,7 +60,7 @@ def set_test_params(self):
         self.extra_args = [
             [],
             ["-fastprune", "-prune=1", "-blockfilterindex=1", "-coinstatsindex=1"],
-            ["-txindex=1", "-blockfilterindex=1", "-coinstatsindex=1"],
+            ["-persistmempool=0","-txindex=1", "-blockfilterindex=1", "-coinstatsindex=1"],
         ]
 
     def setup_network(self):
@@ -135,6 +135,19 @@ def expected_error(log_msg="", error_msg=""):
         rmtree(chainstate_snapshot_path)
         self.start_node(0)
 
+    def test_invalid_mempool_state(self, dump_output_path):
+        self.log.info("Test bitcoind should fail when mempool not empty.")
+        node=self.nodes[2]
+        tx = MiniWallet(node).send_self_transfer(from_node=node)
+
+        assert tx['txid'] in node.getrawmempool()
+
+        # Attempt to load the snapshot on Node 2 and expect it to fail
+        with node.assert_debug_log(expected_msgs=["[snapshot] can't activate a snapshot when mempool not empty"]):
+            assert_raises_rpc_error(-32603, "Unable to load UTXO snapshot", node.loadtxoutset, dump_output_path)
+
+        self.restart_node(2, extra_args=self.extra_args[2])
+
     def run_test(self):
         """
         Bring up two (disconnected) nodes, mine some new blocks on the first,
@@ -197,6 +210,7 @@ def run_test(self):
 
         assert_equal(n0.getblockchaininfo()["blocks"], FINAL_HEIGHT)
 
+        self.test_invalid_mempool_state(dump_output['path'])
         self.test_invalid_snapshot_scenarios(dump_output['path'])
         self.test_invalid_chainstate_scenarios()