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tests: test unilateral closing with unknown fees + cpfp with withdraw #8879

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tests: test unilateral closing with unknown fees + cpfp with `withdraw`
enaples Feb 4, 2026
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tests: fix comment
enaples Feb 4, 2026
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94 changes: 94 additions & 0 deletions tests/test_closing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,100 @@
import unittest


@unittest.skipIf(TEST_NETWORK != 'regtest', 'Uses regtest')
def test_close_unknownfees_cpfp(node_factory, bitcoind):
"""Open a channel, make a payment, close it when CLN cannot estimate fees,
then use withdraw as CPFP to bump the closing transaction."""

# l1 cannot estimate fees (dev-no-fake-fees + mocked estimatesmartfee error).
# We start it stopped so we can install the mock before startup.
opts = {
'feerates': None,
'dev-no-fake-fees': True,
}

l1, l2 = node_factory.get_nodes(2, opts=[opts, {}])
l1.fundwallet(10**7)
l2.fundwallet(10**7)

# Verify fee estimation is failing only on l1
l1.daemon.wait_for_log('Unable to estimate any fees')

# l1 can't open channels (no fee estimates), so l2 opens to l1.
l2.rpc.connect(l1.info['id'], 'localhost', l1.port)
l2.rpc.fundchannel(l1.info['id'], 10**6, minconf=0)

# Mine funding and verify channel is active.
bitcoind.generate_block(1, wait_for_mempool=1)
l2.daemon.wait_for_log(r'CHANNELD_NORMAL')

# Make some payment while mining some blocks.
for i in range(10):
l2.pay(l1, 10**5)
bitcoind.generate_block(1)
sync_blockheight(bitcoind, [l1, l2])

l2.stop()

# l1 initiates unilateral close while l2 is offline.
close = l1.rpc.close(l2.info['id'], 1)
close_txid = only_one(close['txids'])

wait_for(lambda: close_txid in bitcoind.rpc.getrawmempool())

# The closing tx should appear in the mempool.
assert close_txid in bitcoind.rpc.getrawmempool()

# `bitcoind.generate_block` expects a `needfeerate` in sat/kW
mempool_details = bitcoind.rpc.getrawmempool(True)
close_fees = float(mempool_details[close_txid]['fees']['ancestor'])
close_vsize = float(mempool_details[close_txid]['ancestorsize'])
close_feerate = close_fees * 10**8 / (close_vsize * 4 / 1000)

# Create 1 block but exclude the closing tx (feerate too low).
bitcoind.generate_block(1, needfeerate=close_feerate + 1)

# Verify the close tx is still unconfirmed in the mempool.
assert close_txid in bitcoind.rpc.getrawmempool()

l1_close_out = only_one([o for o in l1.rpc.listfunds()['channels']
if o['peer_id'] == l2.info['id']])
assert l1_close_out['state'] == 'AWAITING_UNILATERAL'

# Now perform CPFP: spend the unconfirmed close output using withdraw
# with an explicit feerate and minconf=0 to allow spending unconfirmed.
cpfp_addr = l1.rpc.newaddr()['p2tr']

# Withdraw should fail without
with pytest.raises(RpcError, match=r'Cannot estimate fees \(yet\)'):
l1.rpc.withdraw(cpfp_addr, 'all')

# Withdraw should succed
cpfp_txid = l1.rpc.withdraw(cpfp_addr, 'all', '1perkb', minconf=0)['txid']

# There should now be two transactions in the mempool: the close tx and
# the CPFP child tx that spends from it.
wait_for(lambda: len(bitcoind.rpc.getrawmempool()) > 1)
mempool_after = bitcoind.rpc.getrawmempool()
assert close_txid in mempool_after

# Mine both transactions.
bitcoind.generate_block(1, wait_for_mempool=2)

# l1 should see the CPFP output as confirmed.
wait_for(lambda: all(o['status'] == 'confirmed' and o['txid'] == cpfp_txid
for o in l1.rpc.listfunds()['outputs']))

# Start l2
l2.start()

# Why l1 does not connect with l2 after channel close?
# Verify l2 should see the channel as closed onchain.
wait_for(lambda: all(o['state'] == 'ONCHAIN'
for o in l2.rpc.listfunds()['channels']
if o['peer_id'] == l1.info['id']))


def test_closing_simple(node_factory, bitcoind, chainparams):
coin_mvt_plugin = os.path.join(os.getcwd(), 'tests/plugins/coin_movements.py')
l1, l2 = node_factory.line_graph(2, opts={'plugin': coin_mvt_plugin})
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