Add Tests for command line arguments

[lholmquist]

When i was adding in the tests for the --list-subsystem flag, i noticed that there were no tests for the other command line flags.

Now that there is a test for list-subsystems(which has affected the code coverage), there should probably be tests for the other commands

Instead of creating separate issues for each command, this issue is to track the addition of those other tests.

• [ ] usage
• [ ] version
• [ ] validate-metadata
• [ ] tap
• [ ] list
• [x] list-subsystems

I'm happy to continue working on adding these items :)