pytest: Add a test for the plugin option passthrough

Signed-off-by: Christian Decker <@cdecker>

tests/test_plugin.py

@@ -0,0 +1,29 @@
+from fixtures import *  # noqa: F401,F403
+
+import subprocess
+
+
+def test_option_passthrough(node_factory):
+    """ Ensure that registering options works.
+
+    First attempts without the plugin and then with the plugin.
+    """
+    plugin_path = 'contrib/helloworld-plugin/main.py'
+
+    help_out = subprocess.check_output([
+        'lightningd/lightningd',
+        '--help'
+    ]).decode('utf-8')
+    assert('--greeting' not in help_out)
+
+    help_out = subprocess.check_output([
+        'lightningd/lightningd',
+        '--plugin={}'.format(plugin_path),
+        '--help'
+    ]).decode('utf-8')
+    assert('--greeting' in help_out)
+
+    # Now try to see if it gets accepted, would fail to start if the
+    # option didn't exist
+    n = node_factory.get_node(options={'plugin': plugin_path, 'greeting': 'Mars'})
+    n.stop()