feat: Set up comprehensive Python testing infrastructure

[llbbl]

Set up Python Testing Infrastructure

Summary

This PR establishes a complete testing infrastructure for the "40 Algorithms Every Programmer Should Know" Python project. The setup uses Poetry for dependency management and pytest as the testing framework, providing a solid foundation for test-driven development.

Changes Made

Package Management

• ✅ Set up Poetry as the package manager
• ✅ Created pyproject.toml with project configuration
• ✅ Generated poetry.lock for reproducible builds

Testing Dependencies

Added the following development dependencies:

• pytest (^7.4.3) - Core testing framework
• pytest-cov (^4.1.0) - Coverage reporting integration
• pytest-mock (^3.12.0) - Mocking utilities

Testing Configuration

Configured pytest in pyproject.toml with:

• Test discovery patterns for test_*.py and *_test.py files
• Coverage settings with HTML and XML report generation
• Coverage threshold set to 0% initially (adjust as needed)
• Custom markers: unit, integration, and slow
• Strict marker enforcement and verbose output

Directory Structure

tests/
├── __init__.py
├── conftest.py          # Shared fixtures and configuration
├── test_validation.py   # Infrastructure validation tests
├── unit/
│   └── __init__.py
└── integration/
    └── __init__.py

Shared Fixtures (conftest.py)

Created comprehensive fixtures including:

• temp_dir - Temporary directory management
• temp_file - Temporary file creation
• sample_data - Common test data structures
• mock_config - Configuration mocking
• sample_csv_data - CSV file generation
• sample_json_data - JSON file generation
• reset_random_seed - Reproducible test runs
• helpers - Custom assertion utilities

Additional Setup

• Updated .gitignore with Python and testing-related patterns
• Created validation tests to verify the infrastructure works correctly

How to Use

Install Dependencies

poetry install --no-root

Run Tests

# Run all tests
poetry run pytest

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

# Run with coverage report
poetry run pytest --cov

# Run specific test file
poetry run pytest tests/test_validation.py

Writing Tests

1. Place unit tests in tests/unit/
2. Place integration tests in tests/integration/
3. Use fixtures from conftest.py for common operations
4. Mark tests appropriately: @pytest.mark.unit, @pytest.mark.integration, @pytest.mark.slow

Notes

• Python version requirement updated to ^3.8 for compatibility with testing dependencies
• Coverage threshold initially set to 0% to allow gradual improvement
• The project uses --no-root installation as it's a code examples repository without a package structure
• All 10 validation tests pass successfully, confirming the infrastructure is working correctly

Next Steps

1. Adjust coverage threshold in pyproject.toml as more tests are added
2. Add pre-commit hooks for automatic test running
3. Configure CI/CD pipeline to run tests automatically
4. Begin writing actual unit tests for the algorithm implementations