feat: Set up comprehensive Python testing infrastructure with Poetry

[llbbl]

Add Python Testing Infrastructure

Summary

This PR sets up a complete testing infrastructure for the Python course assignments project using Poetry as the package manager and pytest as the testing framework.

Changes Made

Package Management

• Poetry Setup: Initialized Poetry with package-mode = false since this is a collection of assignments rather than a distributable package
• Dependencies: Added testing dependencies as development dependencies:
  • pytest ^8.3.0 - Core testing framework
  • pytest-cov ^6.0.0 - Coverage reporting
  • pytest-mock ^3.14.0 - Mocking utilities

Testing Configuration

• pytest Configuration in pyproject.toml:

  • Strict markers and configuration enforcement
  • Coverage reporting with 80% threshold
  • HTML and XML coverage report generation
  • Custom markers: unit, integration, slow
  • Test discovery patterns configured

• Coverage Configuration:

  • Source set to tests directory only (excluding course assignments)
  • Comprehensive omit patterns
  • Branch coverage enabled
  • Multiple report formats

Directory Structure

tests/
├── __init__.py
├── conftest.py          # Shared fixtures and configuration
├── test_setup_validation.py  # Validation tests
├── unit/
│   └── __init__.py
└── integration/
    └── __init__.py

Shared Fixtures (in conftest.py)

• temp_dir - Temporary directory management
• mock_config - Sample configuration data
• sample_data - Test data for assignments
• reset_environment - Environment cleanup (autouse)
• mock_file_content - Sample file content
• capture_stdout - Print statement capture
• project_root - Project root path helper

Additional Updates

• .gitignore: Updated with comprehensive Python, testing, and Claude-specific entries
• CLAUDE.md: Initialized for project context
• Validation Tests: Created to verify the infrastructure works correctly

How to Use

Installation

# Install Poetry (if not already installed)
curl -sSL https://install.python-poetry.org | python3 -

# Install dependencies
poetry install

Running Tests

# Run all tests with coverage
poetry run pytest

# Run specific test markers
poetry run pytest -m unit
poetry run pytest -m integration
poetry run pytest -m "not slow"

# Run with specific options
poetry run pytest -v --no-cov  # Verbose without coverage
poetry run pytest tests/unit/  # Run only unit tests

Writing Tests

1. Create test files in tests/unit/ or tests/integration/
2. Use the test_ prefix for test files and functions
3. Import shared fixtures from conftest.py
4. Apply appropriate markers (@pytest.mark.unit, etc.)

Coverage Reports

• Terminal: Shown automatically after test runs
• HTML: Open htmlcov/index.html in a browser
• XML: Available at coverage.xml for CI/CD integration

Notes

• Poetry is configured with package-mode = false since this is a course assignment collection, not a package
• Coverage is configured to only analyze test files, not the course assignments
• The 80% coverage threshold applies only to the test infrastructure itself
• All Python assignment files remain untouched and are excluded from coverage