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Python Package Development & Testing Overview

This guide outlines the structure and tools commonly used in Python package development, with a focus on managing dependencies, testing, and configuration.

📦 Dependency Management

requirements.txt

• Lists production dependencies required to run the Python application.
• Installed in production environments to keep builds minimal and fast.

requirements_dev.txt

• Lists development and testing dependencies.
• Used by developers to set up a full-featured environment including tools for testing, linting, etc.

⚙️ Project Configuration

setup.cfg

• Used by setuptools to define package metadata and installation behavior.
• Contains:
  • Package name, version, author, license
  • Dependencies
  • Entry points
  • Metadata for PyPI

pyproject.toml

• A modern configuration file introduced by PEP 518.
• Defines the build system and can replace setup.cfg.
• Compatible with tools like Poetry, Flit, and modern setuptools.

🧪 Testing

🔍 Testing Types

• Manual Testing: Done by a human to check functionality.
• Automated Testing: Code-based testing, executed automatically.

🧱 Modes of Testing

• Unit Testing: Tests individual components or functions in isolation.
• Integration Testing: Ensures different modules or services work together.

🧪 Testing Frameworks

Framework	Purpose
pytest	Simple and powerful testing tool
unittest	Built-in Python testing framework
robotframework	For acceptance testing
selenium	UI/browser testing
behave	BDD (Behavior Driven Development)
doctest	Test code embedded in docstrings

📁 Linting & Code Quality

Tools for Style Checking

• pylint – Comprehensive linting
• flake8 – Combines:
  • pycodestyle (PEP8 checks)
  • pyflakes (error detection)
  • mccabe (complexity checking)

🔄 Testing Automation with tox

What is tox?

• Automates testing across multiple Python versions.
• Creates isolated virtual environments.
• Installs dependencies and runs defined commands.

How tox Works:

• Creates isolated environments with virtualenv
• Installs dev and test dependencies
• Runs test and lint commands
• Outputs results for each environment

tox vs others:

• It's like a combination of virtualenvwrapper + Makefile functionality.

🧪 Example tox.ini

[tox]
envlist = py38, py39, lint

[testenv]
deps = 
    pytest
commands = 
    pytest tests/

[testenv:lint]
deps = 
    flake8
commands = 
    flake8 package_name/