pytest: Add a test for the JSON-RPC passthrough

Tests JSON-RPC registration, as well as success and failures.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

tests/test_plugin.py

@@ -1,5 +1,7 @@
 from fixtures import *  # noqa: F401,F403
+from lightning import RpcError
 
+import pytest
 import subprocess
 
 
@@ -27,3 +29,25 @@ def test_option_passthrough(node_factory):
     # option didn't exist
     n = node_factory.get_node(options={'plugin': plugin_path, 'greeting': 'Mars'})
     n.stop()
+
+
+def test_rpc_passthrough(node_factory):
+    """Starting with a plugin exposes its RPC methods.
+
+    First check that the RPC method appears in the help output and
+    then try to call it.
+
+    """
+    plugin_path = 'contrib/plugins/helloworld.py'
+    n = node_factory.get_node(options={'plugin': plugin_path, 'greeting': 'Mars'})
+
+    # Make sure that the 'hello' command that the helloworld.py plugin
+    # has registered is available.
+    cmd = [hlp for hlp in n.rpc.help()['help'] if 'hello' in hlp['command']]
+    assert(len(cmd) == 1)
+
+    # Now try to call it and see what it returns:
+    greet = n.rpc.hello(name='Sun')
+    assert(greet == "Hello Sun")
+    with pytest.raises(RpcError):
+        n.rpc.fail()