Add more unit tests for the cli module

[havanagrawal]

Problem

Unit test coverage for the cli is quite spotty. Add unit tests to test the different flags and arguments passed to the CLI

Prerequisites

• You know basic git, i.e. how to fork this repo, clone this repo, work on a branch and send a PR
• You have basic working knowledge of Python
• You are able to run Python on your machine
• You are familiar, or are willing to learn, how to patch/mock functions, write and run unit tests in Python.

Hints

Take a look at the already written tests, and start from there.

[rishm069]

Hi! May I work on this one?