def plugin(plugin_without_server):
    """
    Construct mock plugin with NotebookClient with server registered.

    Use `plugin.client` to access the client.
    """
    server_info = {'notebook_dir': '/path/notebooks',
                   'url': 'fake_url',
                   'token': 'fake_token'}
    plugin_without_server.client.register(server_info)
    return plugin_without_server