pyln: Allow users to override the LightningNode class

Quite a few of the things in the LightningNode class are tailored to their use
in the c-lightning tests, so I decided to split those customizations out into
a sub-class, and adding one more fixture that just serves the class. This
allows us to override the LightningNode implementation in our own tests, while
still having sane defaults for other users.

contrib/pyln-testing/pyln/testing/fixtures.py

@@ -1,6 +1,6 @@
 from concurrent import futures
 from pyln.testing.db import SqliteDbProvider, PostgresDbProvider
-from pyln.testing.utils import NodeFactory, BitcoinD, ElementsD, env, DEVELOPER
+from pyln.testing.utils import NodeFactory, BitcoinD, ElementsD, env, DEVELOPER, LightningNode
 
 import logging
 import os
@@ -67,6 +67,11 @@ network_daemons = {
 }
 
 
+@pytest.fixture
+def node_cls():
+    return LightningNode
+
+
 @pytest.fixture
 def bitcoind(directory, teardown_checks):
     chaind = network_daemons[env('TEST_NETWORK', 'regtest')]
@@ -145,13 +150,14 @@ def teardown_checks(request):
 
 
 @pytest.fixture
-def node_factory(request, directory, test_name, bitcoind, executor, db_provider, teardown_checks):
+def node_factory(request, directory, test_name, bitcoind, executor, db_provider, teardown_checks, node_cls):
     nf = NodeFactory(
         test_name,
         bitcoind,
         executor,
         directory=directory,
         db_provider=db_provider,
+        node_cls=node_cls
     )
 
     yield nf

contrib/pyln-testing/pyln/testing/utils.py

@@ -465,7 +465,7 @@ class ElementsD(BitcoinD):
 class LightningD(TailableProc):
     def __init__(self, lightning_dir, bitcoindproxy, port=9735, random_hsm=False, node_id=0):
         TailableProc.__init__(self, lightning_dir)
-        self.executable = 'lightningd/lightningd'
+        self.executable = 'lightningd'
         self.lightning_dir = lightning_dir
         self.port = port
         self.cmd_prefix = []
@@ -903,7 +903,7 @@ class LightningNode(object):
 class NodeFactory(object):
     """A factory to setup and start `lightningd` daemons.
     """
-    def __init__(self, testname, bitcoind, executor, directory, db_provider):
+    def __init__(self, testname, bitcoind, executor, directory, db_provider, node_cls):
         self.testname = testname
         self.next_id = 1
         self.nodes = []
@@ -912,6 +912,7 @@ class NodeFactory(object):
         self.directory = directory
         self.lock = threading.Lock()
         self.db_provider = db_provider
+        self.node_cls = node_cls
 
     def split_options(self, opts):
         """Split node options from cli options
@@ -985,7 +986,7 @@ class NodeFactory(object):
         # Get the DB backend DSN we should be using for this test and this
         # node.
         db = self.db_provider.get_db(lightning_dir, self.testname, node_id)
-        node = LightningNode(
+        node = self.node_cls(
             node_id, lightning_dir, self.bitcoind, self.executor, db=db,
             port=port, options=options, **kwargs
         )

tests/fixtures.py

@@ -1,2 +1,19 @@
 from utils import DEVELOPER, TEST_NETWORK  # noqa: F401,F403
 from pyln.testing.fixtures import directory, test_base_dir, test_name, chainparams, node_factory, bitcoind, teardown_checks, db_provider, executor  # noqa: F401,F403
+from pyln.testing import utils
+
+import pytest
+
+
+@pytest.fixture
+def node_cls():
+    return LightningNode
+
+
+class LightningNode(utils.LightningNode):
+    def __init__(self, *args, **kwargs):
+        utils.LightningNode.__init__(self, *args, **kwargs)
+
+        # Yes, we really want to test the local development version, not
+        # something in out path.
+        self.daemon.executable = 'lightningd/lightningd'