b3b9d93fb0
If we grab l2's scratch_txid too early, it might not be the one which goes in the mempool:
```
2025-05-12T05:15:44.3947957Z def test_update_fee_reconnect(node_factory, bitcoind):
...
2025-05-12T05:15:44.3962867Z # Now shutdown cleanly.
2025-05-12T05:15:44.3963253Z l1.rpc.close(chan)
2025-05-12T05:15:44.3963591Z
2025-05-12T05:15:44.3963905Z # And should put closing into mempool.
2025-05-12T05:15:44.3964671Z l1.wait_for_channel_onchain(l2.info['id'])
2025-05-12T05:15:44.3965175Z > l2.wait_for_channel_onchain(l1.info['id'])
2025-05-12T05:15:44.3965496Z
2025-05-12T05:15:44.3965659Z tests/test_connection.py:2634:
...
2025-05-12T05:15:44.3966616Z contrib/pyln-testing/pyln/testing/utils.py:1216: in wait_for_channel_onchain
2025-05-12T05:15:44.3967080Z wait_for(lambda: txid in self.bitcoin.rpc.getrawmempool())
2025-05-12T05:15:44.3967429Z _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
2025-05-12T05:15:44.3967631Z
2025-05-12T05:15:44.3967888Z success = <function LightningNode.wait_for_channel_onchain.<locals>.<lambda> at 0x7f0562d7f0a0>
2025-05-12T05:15:44.3968299Z timeout = 180
2025-05-12T05:15:44.3968408Z
2025-05-12T05:15:44.3968515Z def wait_for(success, timeout=TIMEOUT):
2025-05-12T05:15:44.3968805Z start_time = time.time()
2025-05-12T05:15:44.3969041Z interval = 0.25
2025-05-12T05:15:44.3969251Z while not success():
2025-05-12T05:15:44.3969510Z time_left = start_time + timeout - time.time()
2025-05-12T05:15:44.3969794Z if time_left <= 0:
2025-05-12T05:15:44.3970278Z > raise ValueError("Timeout while waiting for {}".format(success))
2025-05-12T05:15:44.3970894Z E ValueError: Timeout while waiting for <function LightningNode.wait_for_channel_onchain.<locals>.<lambda> at 0x7f0562d7f0a0>
```
pyln-testing: A library to write tests against Core Lightning
This library implements a number of utilities that help building tests for Core Lightning nodes. In particular it provides a number of pytest fixtures that allow the management of a test network of a given topology and then execute a test scenarion.
pyln-testing is used by Core Lightning for its internal tests, and by the
community plugin directory to exercise the plugins.
Installation
pyln-testing is available on pip:
pip install pyln-testing
Alternatively you can also install the development version to get access to currently unreleased features by checking out the Core Lightning source code and installing into your python3 environment:
git clone https://github.com/ElementsProject/lightning.git
cd lightning/contrib/pyln-testing
poetry install
This will add links to the library into your environment so changing the checked out source code will also result in the environment picking up these changes. Notice however that unreleased versions may change API without warning, so test thoroughly with the released version.
Testing GRPC Bindings
The grpc bindings can be tested by setting the CLN_TEST_GRPC=1
environment variable. This will cause the testing framework to use a
grpc client to talk to the cln-grpc plugin, rather than talking
directly to the node's JSON-RPC interface. Since the GRPC related
dependencies are guarded behind a feature flag in pyln-testing
you'll need to install it with the grpc feature enabled in order to
be able to run in this mode.
Below is a diagram of how the normal JSON-RPC interaction looks like, followed by one that display the grpc interaction:
CLN -- JSON-RPC -- LightningRpc -- pytest
\_____CLN_____/ \_______pytest_______/
CLN -- JSON-RPC -- cln-rpc -- rpc2grpc converters -- grpc interface -- python grpc client -- python grpc2json converter -- pytest
\_____CLN_____/ \___________cln-grpc-plugin____________________/ \__________________________pytest________________________/
As you can see the grpc mode attempts to emulate the simple JSON-RPC
mode by passing the call through a number of conversions. The last
step grpc2json is rather incomplete, and will cause quite a few
tests to fail for now, until the conversion is completed and we reach
feature parity between the interaction modes.