Notes on the book Clean Architectures in Python

Recently I came across a book on clean architecture focusing on Python. I was looking for something like this and got it on Leanpub for free. You can get the book from here. What follows is a bullet point list of notes I made while reading the book.

TDD

1. Test first, code later.
2. Add reasonably minimum amount of code to pass tests.
3. Shouldn't have >1 test failing at a time.
4. Write code that passes the test, then refactor it.
5. A new test must fail first. If it doesn't, ask why add it then?
6. Never refactor without tests.

How many assertions?

• If the test is a logical AND between condition, use multiple assertions (eg, positive even number) and if it's a logical OR then write multiple tests.
  Testing bugs and feature requests

• Write tests first to reproduce the bug. If there is no failed test there is no bug.
• First make sure the bug is not related to environments. Clean Architecture
• Clean is Layered
• Spherical in shape
• Inner layers are more abstract
• Layers:
  • Entities
  • Use Cases
  • External Systems
• Interaction between layers:
  • Outer -> Inner = Simple Data Structures
  • Inner -> Outer = Through Interfaces/APIs
• General workflow to plug the architecture in any external system:
  • Initialise the repo.
  • Initialise the use case.
  • Collect the results.