add test helpers / tests for command output

[edaniszewski]

this will likely be a bit of work upfront to get it done right, but once we have one example of how to do it, it should be fairly easy to apply to all commands afterwards.

will likely want to use the idea of "golden files" (for which there are many examples of online)

[timfallmk]

I haven't used "golden files" before, but I think we could go down two other routes as well.

1. Use mocking to create a full test suite.
2. Test against an actual server.

Both come with drawbacks and benefits.