splice-script: Test for msat chan balances

diff --git a/tests/test_splice.py b/tests/test_splice.py
index 00a0f097..b98cd02e 100644
--- a/tests/test_splice.py
+++ b/tests/test_splice.py
@@ -196,6 +196,217 @@ def test_script_splice_in(node_factory, bitcoind, chainparams):
     assert not account_info['account_closed']
 
 
+@pytest.mark.xfail(strict=True)
+@pytest.mark.openchannel('v1')
+@pytest.mark.openchannel('v2')
+@unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')
+def test_script_splice_msat(node_factory, bitcoind, chainparams):
+    # Test splices with msat level sats to confirm rounding
+    fundamt = 1000000
+
+    coin_mvt_plugin = Path(__file__).parent / "plugins" / "coin_movements.py"
+    l1, l2 = node_factory.line_graph(2, fundamount=fundamt, wait_for_announce=True,
+                                     opts={'plugin': coin_mvt_plugin})
+
+    initial_wallet_balance = Millisatoshi(bkpr_account_balance(l1, 'wallet'))
+    initial_channel_balance = Millisatoshi(bkpr_account_balance(l1, first_channel_id(l1, l2)))
+    assert initial_channel_balance == Millisatoshi(fundamt * 1000)
+
+    # Splice in 100k sats into first channel, explicitly taking out 200k sats from wallet
+    # and letting change go automatically back to wallet (100k less onchain fees)
+    spliceamt = 100000
+    withdraw_amt = 200000
+    starting_wallet_msat = withdraw_amt * 10000
+
+    sent_msats = 1111
+    # purposely pay in msats
+    inv = l2.rpc.invoice(sent_msats, '1', 'no_1')
+    l1.rpc.pay(inv['bolt11'])
+    initial_channel_balance -= sent_msats
+
+    l1.rpc.splice(f"wallet -> {withdraw_amt}; {spliceamt} -> *:?", debug_log=True)
+    p1 = only_one(l1.rpc.listpeerchannels(peer_id=l2.info['id'])['channels'])
+    p2 = only_one(l2.rpc.listpeerchannels(l1.info['id'])['channels'])
+    assert p1['inflight'][0]['splice_amount'] == spliceamt
+    assert p1['inflight'][0]['total_funding_msat'] == (fundamt + spliceamt) * 1000
+    assert p1['inflight'][0]['our_funding_msat'] == fundamt * 1000
+    assert p2['inflight'][0]['splice_amount'] == 0
+    assert p2['inflight'][0]['total_funding_msat'] == (fundamt + spliceamt) * 1000
+    assert p2['inflight'][0]['our_funding_msat'] == 0
+    bitcoind.generate_block(6, wait_for_mempool=1)
+    l2.daemon.wait_for_log(r'lightningd, splice_locked clearing inflights')
+
+    p1 = only_one(l1.rpc.listpeerchannels(peer_id=l2.info['id'])['channels'])
+    p2 = only_one(l2.rpc.listpeerchannels(l1.info['id'])['channels'])
+    assert p1['to_us_msat'] == ((fundamt + spliceamt) * 1000) - sent_msats
+    assert p1['total_msat'] == (fundamt + spliceamt) * 1000
+    assert p2['to_us_msat'] == sent_msats
+    assert p2['total_msat'] == (fundamt + spliceamt) * 1000
+    assert 'inflight' not in p1
+    assert 'inflight' not in p2
+
+    wait_for(lambda: len(l1.rpc.listfunds()['outputs']) == 1)
+    wait_for(lambda: len(l1.rpc.listfunds()['channels']) == 1)
+
+    # At the end we'd expect the balance of channel 1 to be up by the splice amount
+    end_channel_balance = Millisatoshi(bkpr_account_balance(l1, first_channel_id(l1, l2)))
+    end_wallet_balance = Millisatoshi(bkpr_account_balance(l1, 'wallet'))
+    assert initial_channel_balance + Millisatoshi(spliceamt * 1000) == end_channel_balance
+
+    # The fee is assumed to be the difference between the start+end balances?
+    fee_guess = initial_wallet_balance + initial_channel_balance - end_channel_balance - end_wallet_balance
+
+    # We'd expect the following coin movements
+    expected_wallet_moves = [
+        #  initial deposit
+        {'type': 'chain_mvt', 'credit_msat': starting_wallet_msat, 'debit_msat': 0, 'tags': ['deposit']},
+        #  channel open spend
+        {'type': 'chain_mvt', 'credit_msat': 0, 'debit_msat': starting_wallet_msat, 'tags': ['withdrawal']},
+        #  channel open change
+        {'type': 'chain_mvt', 'credit_msat': initial_wallet_balance, 'debit_msat': 0, 'tags': ['deposit']},
+        #  splice-in spend
+        {'type': 'chain_mvt', 'debit_msat': initial_wallet_balance, 'credit_msat': 0, 'tags': ['withdrawal']},
+        #  post-splice deposit
+        {'type': 'chain_mvt', 'credit_msat': initial_wallet_balance - Millisatoshi(spliceamt * 1000) - fee_guess, 'debit_msat': 0, 'tags': ['deposit']},
+    ]
+
+    check_coin_moves(l1, 'wallet', expected_wallet_moves, chainparams)
+    expected_channel_moves = [
+        # channel_open  [utxo created], chain_mvt
+        {'type': 'chain_mvt', 'credit_msat': fundamt * 1000, 'debit_msat': 0, 'tags': ['channel_open', 'opener']},
+        # channel payment
+        {'type': 'channel_mvt', 'debit_msat': sent_msats, 'credit_msat': 0, 'tags': ['invoice'], 'fees_msat': 0},
+        # channel_close [utxo spend], chain_mvt     (fundamt)
+        {'type': 'chain_mvt', 'debit_msat': fundamt * 1000 - sent_msats, 'credit_msat': 0, 'tags': ['channel_close', 'splice']},
+        # channel_open  [utxo created], chain_mvt   (fundamt - spliceamt)
+        {'type': 'chain_mvt', 'credit_msat': (fundamt + spliceamt) * 1000 - sent_msats, 'debit_msat': 0, 'tags': ['channel_open', 'opener']},
+    ]
+    check_coin_moves(l1, first_channel_id(l1, l2), expected_channel_moves, chainparams)
+
+    # Make sure the channel isn't marked as closed in bookkeeper
+    account_id = first_channel_id(l1, l2)
+    account_info = only_one([acct for acct in l1.rpc.bkpr_listbalances()['accounts'] if acct['account'] == account_id])
+    assert not account_info['account_closed']
+
+    # We'd also expect the wallet to be down by splice amt + fees
+    onchain_fees = [fee for fee in l1.rpc.bkpr_listincome()['income_events'] if fee['tag'] == 'onchain_fee']
+    assert len(onchain_fees) == 2
+    total_fees = sum([x['debit_msat'] for x in onchain_fees])
+    assert starting_wallet_msat - sent_msats == end_wallet_balance + total_fees + end_channel_balance
+
+    # Now close the channel and check that everything resolves as expected
+    l1.rpc.close(l2.info['id'])
+    l1.wait_for_channel_onchain(l2.info['id'])
+    account_info = only_one([acct for acct in l1.rpc.bkpr_listbalances()['accounts'] if acct['account'] == account_id])
+    assert not account_info['account_closed']
+
+
+@pytest.mark.xfail(strict=True)
+@pytest.mark.openchannel('v1')
+@pytest.mark.openchannel('v2')
+@unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')
+def test_script_splice_msat_roundup(node_factory, bitcoind, chainparams):
+    # Test splices with msat level sats to confirm rounding, using an amount
+    # That would naturally round up (even though we always round down).
+    fundamt = 1000000
+
+    coin_mvt_plugin = Path(__file__).parent / "plugins" / "coin_movements.py"
+    l1, l2 = node_factory.line_graph(2, fundamount=fundamt, wait_for_announce=True,
+                                     opts={'plugin': coin_mvt_plugin})
+
+    initial_wallet_balance = Millisatoshi(bkpr_account_balance(l1, 'wallet'))
+    initial_channel_balance = Millisatoshi(bkpr_account_balance(l1, first_channel_id(l1, l2)))
+    assert initial_channel_balance == Millisatoshi(fundamt * 1000)
+
+    # Splice in 100k sats into first channel, explicitly taking out 200k sats from wallet
+    # and letting change go automatically back to wallet (100k less onchain fees)
+    spliceamt = 100000
+    withdraw_amt = 200000
+    starting_wallet_msat = withdraw_amt * 10000
+
+    sent_msats = 1999
+    # purposely pay in msats
+    inv = l2.rpc.invoice(sent_msats, '1', 'no_1')
+    l1.rpc.pay(inv['bolt11'])
+    initial_channel_balance -= sent_msats
+
+    l1.rpc.splice(f"wallet -> {withdraw_amt}; {spliceamt} -> *:?", debug_log=True)
+    p1 = only_one(l1.rpc.listpeerchannels(peer_id=l2.info['id'])['channels'])
+    p2 = only_one(l2.rpc.listpeerchannels(l1.info['id'])['channels'])
+    assert p1['inflight'][0]['splice_amount'] == spliceamt
+    assert p1['inflight'][0]['total_funding_msat'] == (fundamt + spliceamt) * 1000
+    assert p1['inflight'][0]['our_funding_msat'] == fundamt * 1000
+    assert p2['inflight'][0]['splice_amount'] == 0
+    assert p2['inflight'][0]['total_funding_msat'] == (fundamt + spliceamt) * 1000
+    assert p2['inflight'][0]['our_funding_msat'] == 0
+    bitcoind.generate_block(6, wait_for_mempool=1)
+    l2.daemon.wait_for_log(r'lightningd, splice_locked clearing inflights')
+
+    p1 = only_one(l1.rpc.listpeerchannels(peer_id=l2.info['id'])['channels'])
+    p2 = only_one(l2.rpc.listpeerchannels(l1.info['id'])['channels'])
+    assert p1['to_us_msat'] == ((fundamt + spliceamt) * 1000) - sent_msats
+    assert p1['total_msat'] == (fundamt + spliceamt) * 1000
+    assert p2['to_us_msat'] == sent_msats
+    assert p2['total_msat'] == (fundamt + spliceamt) * 1000
+    assert 'inflight' not in p1
+    assert 'inflight' not in p2
+
+    wait_for(lambda: len(l1.rpc.listfunds()['outputs']) == 1)
+    wait_for(lambda: len(l1.rpc.listfunds()['channels']) == 1)
+
+    # At the end we'd expect the balance of channel 1 to be up by the splice amount
+    end_channel_balance = Millisatoshi(bkpr_account_balance(l1, first_channel_id(l1, l2)))
+    end_wallet_balance = Millisatoshi(bkpr_account_balance(l1, 'wallet'))
+    assert initial_channel_balance + Millisatoshi(spliceamt * 1000) == end_channel_balance
+
+    # The fee is assumed to be the difference between the start+end balances?
+    fee_guess = initial_wallet_balance + initial_channel_balance - end_channel_balance - end_wallet_balance
+
+    # We'd expect the following coin movements
+    expected_wallet_moves = [
+        #  initial deposit
+        {'type': 'chain_mvt', 'credit_msat': starting_wallet_msat, 'debit_msat': 0, 'tags': ['deposit']},
+        #  channel open spend
+        {'type': 'chain_mvt', 'credit_msat': 0, 'debit_msat': starting_wallet_msat, 'tags': ['withdrawal']},
+        #  channel open change
+        {'type': 'chain_mvt', 'credit_msat': initial_wallet_balance, 'debit_msat': 0, 'tags': ['deposit']},
+        #  splice-in spend
+        {'type': 'chain_mvt', 'debit_msat': initial_wallet_balance, 'credit_msat': 0, 'tags': ['withdrawal']},
+        #  post-splice deposit
+        {'type': 'chain_mvt', 'credit_msat': initial_wallet_balance - Millisatoshi(spliceamt * 1000) - fee_guess, 'debit_msat': 0, 'tags': ['deposit']},
+    ]
+
+    check_coin_moves(l1, 'wallet', expected_wallet_moves, chainparams)
+    expected_channel_moves = [
+        # channel_open  [utxo created], chain_mvt
+        {'type': 'chain_mvt', 'credit_msat': fundamt * 1000, 'debit_msat': 0, 'tags': ['channel_open', 'opener']},
+        # channel payment
+        {'type': 'channel_mvt', 'debit_msat': sent_msats, 'credit_msat': 0, 'tags': ['invoice'], 'fees_msat': 0},
+        # channel_close [utxo spend], chain_mvt     (fundamt)
+        {'type': 'chain_mvt', 'debit_msat': fundamt * 1000 - sent_msats, 'credit_msat': 0, 'tags': ['channel_close', 'splice']},
+        # channel_open  [utxo created], chain_mvt   (fundamt - spliceamt)
+        {'type': 'chain_mvt', 'credit_msat': (fundamt + spliceamt) * 1000 - sent_msats, 'debit_msat': 0, 'tags': ['channel_open', 'opener']},
+    ]
+    check_coin_moves(l1, first_channel_id(l1, l2), expected_channel_moves, chainparams)
+
+    # Make sure the channel isn't marked as closed in bookkeeper
+    account_id = first_channel_id(l1, l2)
+    account_info = only_one([acct for acct in l1.rpc.bkpr_listbalances()['accounts'] if acct['account'] == account_id])
+    assert not account_info['account_closed']
+
+    # We'd also expect the wallet to be down by splice amt + fees
+    onchain_fees = [fee for fee in l1.rpc.bkpr_listincome()['income_events'] if fee['tag'] == 'onchain_fee']
+    assert len(onchain_fees) == 2
+    total_fees = sum([x['debit_msat'] for x in onchain_fees])
+    assert starting_wallet_msat - sent_msats == end_wallet_balance + total_fees + end_channel_balance
+
+    # Now close the channel and check that everything resolves as expected
+    l1.rpc.close(l2.info['id'])
+    l1.wait_for_channel_onchain(l2.info['id'])
+    account_info = only_one([acct for acct in l1.rpc.bkpr_listbalances()['accounts'] if acct['account'] == account_id])
+    assert not account_info['account_closed']
+
+
 @pytest.mark.openchannel('v1')
 @pytest.mark.openchannel('v2')
 @unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')