Open the JavaScript console to watch log output.
Connect to your PostgreSQL database and publish an event:
SELECT pg_notify('crossbar_pubsub_event', json_build_object( 'type', 'direct', 'topic', 'com.example.topic1', 'args', json_build_array(23, 7, 'hello world!'), 'kwargs', json_build_object('foo', 'bar', 'baz', 42) )::text );
You should see the event being received in JavaScript.