pytest: thoroughly test plugin death during startup.

We modify broken.py to be able to fail at different points,
and test that during startup.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/plugins/broken.py

@@ -2,18 +2,27 @@
 """Simple plugin to test that lightningd doesnt crash if it starts a
 misbehaving plugin via RPC.
 """
-
 from pyln.client import Plugin
-import an_unexistent_module_that_will_make_me_crash
-
-plugin = Plugin(dynamic=False)
+import os
+plugin = Plugin()
+crash_at = os.environ.get("BROKEN_CRASH", "before_start")
 
 
 @plugin.init()
 def init(options, configuration, plugin):
     plugin.log("broken.py initializing {}".format(configuration))
-    # We need to actually use the import to pass source checks..
-    an_unexistent_module_that_will_make_me_crash.hello()
+    assert crash_at == "during_init"
+    plugin.does_not_exist()
 
 
+@plugin.method("test_broken")
+def test_broken():
+    return {}
+
+
+if crash_at == "before_start":
+    assert False
+elif crash_at == "during_getmanifest":
+    del plugin.methods['getmanifest']
+
 plugin.run()

tests/test_plugin.py

@@ -300,6 +300,19 @@ def test_plugin_command(node_factory):
     n.rpc.stop()
 
 
+@pytest.mark.xfail(strict=True)
+def test_plugin_fail_on_startup(node_factory):
+    for crash in ('during_init', 'before_start', 'during_getmanifest'):
+        os.environ['BROKEN_CRASH'] = crash
+        n = node_factory.get_node(options={'plugin': os.path.join(os.getcwd(), "tests/plugins/broken.py")})
+        # This can happen before 'Server started with public key' msg
+        n.daemon.logsearch_start = 0
+        n.daemon.wait_for_log('plugin-broken.py: Traceback')
+
+    # Make sure they don't die *after* the message!
+    time.sleep(30)
+
+
 def test_plugin_disable(node_factory):
     """--disable-plugin works"""
     plugin_dir = os.path.join(os.getcwd(), 'contrib/plugins')