Testing with Command Line Arguments and 'slex' Function

How do you test the argument parsing bit of an application that uses argparse?

This episode covers:

• Design for Test: Structuring your app or script so it's easier to test.
• pytest & capsys for testing stdout
• Adding debug and preview flags for debugging and testing
• And reverting to subprocess.run if you can't modify the code under test

Also, there's a full writeup and code samples available:

• Blog post: Testing argparse Applications 
• Code Repo