testsubmit.py sends http requests to jobe on port 80, using the variable JOBE_SERVER as the jobe host name. If nginx (or whatever web server you're using) isn't configured correctly on the Jobe host, the http requests will fail. So if you copy testsubmit.py to another machine (e.g. your moodle server), change JOBE_SERVER to the Jobe host name, and run testsubmit.py, you're testing the full Jobe functionality.
A simple initial sanity test is to point a web browser at the url
http://<jobeserver>/jobe/index.php/restapi/languages
You should get back a JSON response like
[["c","7.3.0"],["cpp","7.3.0"],["java","10.0.1"],["matlab","9.3.0.713579"],["nodejs","8.10.0"],["octave","4.2.2"],["pascal","3.0.4"],["php","7.2.7"],["python2","2.7.15"],["python3","3.6.5"]]This won't work if API key security is turned on but that's not usually appropriate anyway.
Make sure before trying any of the above that the Jobe firewall is off, or at least is allowing connections from whatever machine you testing from.