Function test_lockup_drain

tests/test_pay.py:2613–2634

Try to get channel into a state where opener can't afford fees on additional HTLC, so peer can't add HTLC

(node_factory, bitcoind)

@unittest.skipIf(True, "Test is extremely flaky")
@unittest.skipIf(not DEVELOPER and VALGRIND, "Doesn't raise exception, needs better sync")
def test_lockup_drain(node_factory, bitcoind):
    """Try to get channel into a state where opener can't afford fees on additional HTLC, so peer can't add HTLC"""
    l1, l2 = node_factory.line_graph(2, opts={'may_reconnect': True})

    # l1 sends all the money to l2 until even 1 msat can't get through.
    total = l1.drain(l2)

    # Even if feerate now increases 2x (30000), l2 should be able to send
    # non-dust HTLC to l1.
    l1.force_feerates(30000)
    l2.pay(l1, total // 2)

    # reset fees and send all back again
    l1.force_feerates(15000)
    l1.drain(l2)

    # But if feerate increase just a little more, l2 should not be able to send
    # non-fust HTLC to l1
    l1.force_feerates(30002)  # TODO: Why does 30001 fail? off by one in C code?
    wait_for(lambda: l1.rpc.listpeers()['peers'][0]['connected'])
    with pytest.raises(RpcError, match=r".*Capacity exceeded.*"):
        l2.pay(l1, total // 2)


@pytest.mark.developer("needs DEVELOPER=1 for dev_ignore_htlcs")