Mongo DB Upgrade 3.0 to 3.2 Verification of Upgrade
Can I programatically verify that the upgrade was successful by looking at any metadata from the DB itself?

Yes, you can use shell scripts to redirect input/output of a mongo shell.

Beware that scripted mongo shell behaves differently than the interactive mongo shell: https://docs.mongodb.com/manual/tutorial/write-scripts-for-the-mongo-shell/#differences-between-interactive-and-scripted-mongo

a tangential question, YAML is current preferred config file format, as it is supported even with 4.2 any issues continuing with it?

From https://docs.mongodb.com/manual/reference/configuration-options/ :


  Changed in version 2.6: MongoDB 2.6 introduced a YAML-based
  configuration file format. The 2.4 configuration file format remains
  for backward compatibility.
  
  MongoDB configuration files use the YAML format.


With YAML being the official format, there is no issue. The old format was deprecated, it should still work, but I wouldn't bet that this will never be removed in the future.



About the upgrade procedure (as described here), I imagine you should evaluate the result of rs.status(), but as you are running standalone, I see why you use asserts from db.serverStatus(). In your case, I would be more worried when restarting the mongod process, an exit code was returned.