Write Tests + Implement TDD

**Is your feature request related to a problem? Please describe.**
Currently we only do basic tests - security, deployment checks, and some unit tests.

**Describe the solution you'd like**
We should write more comprehensive unit tests and implement [test driven development](https://news.codecademy.com/test-driven-development/) - where we write the tests first and then write the code.

**Describe alternatives you've considered**
_A clear and concise description of any alternative solutions or features you've considered._
TO DO

**Additional context**

Light reading on the same:
- https://medium.freecodecamp.org/isnt-tdd-test-driven-development-twice-the-work-why-should-you-care-4ddcabeb3df9
- https://medium.com/@solidi/8-observations-on-test-driven-development-a9b5144f868
- https://www.obeythetestinggoat.com/pages/book.html#toc
- https://www.youtube.com/watch?v=_rLPDxpXIFc

We'll also need the technologists to go through quick courses on how to do this well in Django.