test: fix intermittent issue in `feature_bip68_sequence`

To avoid `bad-txns-premature-spend-of-coinbase` error,
when getting a utxo (using `get_utxo`) to create a new
transaction `get_utxo` shouldn't return by default
immature coinbase.

3 files changed, 5 insertions, 2 deletions

diff --git a/test/functional/mempool_compatibility.py b/test/functional/mempool_compatibility.py
index a7bdc49695..7337802aea 100755
--- a/test/functional/mempool_compatibility.py
+++ b/test/functional/mempool_compatibility.py
@@ -47,12 +47,12 @@ class MempoolCompatibilityTest(BitcoinTestFramework):
         # unbroadcasted_tx won't pass old_node's `MemPoolAccept::PreChecks`.
         self.connect_nodes(0, 1)
         self.sync_blocks()
-        self.stop_node(1)
 
         self.log.info("Add a transaction to mempool on old node and shutdown")
         old_tx_hash = new_wallet.send_self_transfer(from_node=old_node)["txid"]
         assert old_tx_hash in old_node.getrawmempool()
         self.stop_node(0)
+        self.stop_node(1)
 
         self.log.info("Move mempool.dat from old to new node")
         old_node_mempool = os.path.join(old_node.datadir, self.chain, 'mempool.dat')
diff --git a/test/functional/mempool_persist.py b/test/functional/mempool_persist.py
index f818801136..8f74d9de20 100755
--- a/test/functional/mempool_persist.py
+++ b/test/functional/mempool_persist.py
@@ -191,6 +191,7 @@ class MempoolPersistTest(BitcoinTestFramework):
     def test_persist_unbroadcast(self):
         node0 = self.nodes[0]
         self.start_node(0)
+        self.start_node(2)
 
         # clear out mempool
         self.generate(node0, 1, sync_fun=self.no_op)
diff --git a/test/functional/test_framework/wallet.py b/test/functional/test_framework/wallet.py
index 64606b818b..90f7275b44 100644
--- a/test/functional/test_framework/wallet.py
+++ b/test/functional/test_framework/wallet.py
@@ -218,10 +218,12 @@ class MiniWallet:
         txid: get the first utxo we find from a specific transaction
         """
         self._utxos = sorted(self._utxos, key=lambda k: (k['value'], -k['height']))  # Put the largest utxo last
+        blocks_height = self._test_node.getblockchaininfo()['blocks']
+        mature_coins = list(filter(lambda utxo: not utxo['coinbase'] or COINBASE_MATURITY - 1 <= blocks_height - utxo['height'], self._utxos))
         if txid:
             utxo_filter: Any = filter(lambda utxo: txid == utxo['txid'], self._utxos)
         else:
-            utxo_filter = reversed(self._utxos)  # By default the largest utxo
+            utxo_filter = reversed(mature_coins)  # By default the largest utxo
         if vout is not None:
             utxo_filter = filter(lambda utxo: vout == utxo['vout'], utxo_filter)
         index = self._utxos.index(next(utxo_filter))