How do we unit test it?

I would like to add tests for my command line parser.
How de we do it? Is there a sample about how to do this properly?

My goal **is not** to test the whole application, of course (since I'm talking about unit testing), but only that a given command line (string) will fire the expected handler with the correct parameters.

I would also want to emphasize on testing invalid inputs, too.

Thanks in advance and congratulations. This is a great library!