pytest: more flakes with "lucky sigs" in coinmoves.
What the developer wrote
Authored by Rusty Russell
pytest: more flakes with "lucky sigs" in coinmoves.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
What changed, and why it matters
This commit only updates test code to handle variable Bitcoin transaction fees caused by signature size differences. It does not change any production code, so it has no security impact on users running Core Lightning.
No action required; this is a test-only reliability fix.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The patch modifies tests/test_coinmoves.py to compute expected coin-move amounts dynamically from bitcoind.rpc.gettxout() rather than hardcoding values. The change addresses test flakiness (‘flakes’) when ECDSA signatures happen to be smaller (‘lucky sigs’), changing the change output value. No node logic, wallet handling, or protocol behavior is altered.
Changed components
tests/test_coinmoves.pyInspect captured patch +10 / −6
diff --git a/tests/test_coinmoves.py b/tests/test_coinmoves.py
index 21f6dea8..7d86ae6c 100644
--- a/tests/test_coinmoves.py
+++ b/tests/test_coinmoves.py
@@ -889,18 +889,19 @@ def test_coinmoves_unilateral_htlc_timeout(node_factory, bitcoind):
expected_chain1 += [{'account_id': 'wallet',
'blockheight': 115,
'credit_msat': 0,
- 'debit_msat': 15579000,
+ 'debit_msat': anchor_change_msats,
'extra_tags': [],
- 'output_msat': 15579000,
+ 'output_msat': anchor_change_msats,
'primary_tag': 'withdrawal',
'spending_txid': htlc_timeout_txid,
'utxo': f"{anchor_spend_txid}:0"},
+ # Change
{'account_id': 'wallet',
'blockheight': 115,
- 'credit_msat': 6358000,
+ 'credit_msat': (15579000 + 6358000) - anchor_change_msats,
'debit_msat': 0,
'extra_tags': [],
- 'output_msat': 6358000,
+ 'output_msat': (15579000 + 6358000) - anchor_change_msats,
'primary_tag': 'deposit',
'utxo': f"{htlc_timeout_txid}:1"},
{'account_id': fundchannel['channel_id'],
@@ -1500,6 +1501,9 @@ def test_coinmoves_unilateral_htlc_fulfilled_oneside(node_factory, bitcoind):
line = l1.daemon.is_in_log('Tracking output.*/OUTPUT_TO_THEM')
to_l2 = int(re.search(r'output [0-9a-f]{64}:([0-9]):', line).group(1))
+ # Usually 16186000, but if we're lucky it's 16193000
+ anchor_change_msats = bitcoind.rpc.gettxout(anchor_spend_txid, 0)['value'] * 100_000_000_000
+
expected_chain1 += [{'account_id': 'wallet', # Anchor spend from fundchannel change
'blockheight': 104,
'credit_msat': 0,
@@ -1511,10 +1515,10 @@ def test_coinmoves_unilateral_htlc_fulfilled_oneside(node_factory, bitcoind):
'utxo': f"{fundchannel['txid']}:{fundchannel['outnum'] ^ 1}"},
{'account_id': 'wallet', # Change from anchor spend
'blockheight': 104,
- 'credit_msat': 16186000,
+ 'credit_msat': anchor_change_msats,
'debit_msat': 0,
'extra_tags': [],
- 'output_msat': 16186000,
+ 'output_msat': anchor_change_msats,
'primary_tag': 'deposit',
'utxo': f"{anchor_spend_txid}:0"},
{'account_id': fundchannel['channel_id'],
Why this scored 15/100
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