⏩ Parallel Change Kata ⏩

Resources

These requirements and the initial state of the code are extracted from the original GitHub repository

What is parallel change?

Parallel change is a technique used in refactoring to make a series of incremental changes to a codebase without breaking the existing code.

It involves three steps:

1. Expand: Add new functionality to the codebase. It can be a class, method, variable... Try to create new code instead of modifying existing implementations, also is a good idea to make new tests for this expanded code even if duplicates previous test behaviors.
2. Migrate: Move the existing code to the new functionality.
3. Contract: Remove the old code.

Description

The kata contains two files:

1. field: the public interface of the code needs to stay as is, but the internal behavior of the class will change by adding a field class that will allow the ShoppingCart class to manage more than one item.
2. method: we want to introduce a new method in the AuthenticationService and deprecate the existing one without breaking the code in the process.

During the refactoring, we need to focus on:

1. Tests must be always green.
2. Use IDE refactor tools when possible.

Note

The final state of the code after making both refactors are under two tags: one for the field scenario and the other for the method scenario.

Objective

The main objective of the kata is to gain a deeper understanding of the parallel change technique and improve the ability to refactor legacy code.

Important

We don't look for the code to be ultra-refactored creating new abstractions, design patterns, etc. Remember, we want to practice the parallel change process.

Configuration

The project can be configured either by using pip or pipenv. Both ways will be explained.

Using pip

1. Create a virtual environment:

   python -m venv .venv

2. Activate the virtual environment:

   source .venv/bin/activate # Linux / Mac
   .venv\Scripts\activate # Windows

3. Install the dependencies:

   pip install -r requirements.txt

Using pipenv

1. Install pipenv:

   pip install pipenv

2. Create a virtual environment with desire python version

   pipenv --python 3.11

   By default it will create the virtual environment outside the project. To create it inside the project, use the following command:

   PIPENV_VENV_IN_PROJECT=1 pipenv --python 3.11

3. Install the dependencies:

   pipenv install

Running the tests

To run the tests, execute one of the following commands:

pytest

or

pipenv run test

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