OpenVPN: test security from external point of view

How would I test an OpenVPN environment from external, kind of black box pentest. I have the public server-IP (port 1194, udp, tun).

I have found NO online ressources on how to do that, or whether some tools are available (e.g. for IPsec there is the ike-scan tools), nmap has no scripts for that, metasploit has no plugins, kali has no tools (only OpenVAS looks like it has a module, didnt try that yet).

Is there any way to test or analyse the security of OpenVPN from an external point of view?