feat: Set up complete Python testing infrastructure with Poetry

[llbbl]

Add Python Testing Infrastructure

Summary

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

Changes Made

Package Management

• Poetry Setup: Created pyproject.toml with Poetry configuration
• Dependencies: Added testing dependencies as development dependencies:
  • pytest (^7.4.0) - Main testing framework
  • pytest-cov (^4.1.0) - Coverage reporting
  • pytest-mock (^3.11.0) - Mocking utilities

Testing Configuration

• pytest Configuration:
  • Test discovery patterns for test_*.py and *_test.py files
  • Coverage reporting with HTML, XML, and terminal output
  • Custom markers: unit, integration, and slow
  • Strict mode enabled with verbose output
  • Coverage threshold set to 0% initially (with note to increase to 80%)

Directory Structure

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

Shared Fixtures (conftest.py)

• temp_dir: Creates temporary directories for test files
• sample_data_file: Creates sample data files for testing
• mock_config: Provides mock configuration dictionaries
• sample_dataset: Provides sample ML datasets
• sample_matrix: Provides sample 2D matrices
• reset_environment: Resets environment variables between tests
• capture_stdout: Captures stdout for testing print statements

Development Commands

• poetry run test - Run all tests with coverage
• poetry run tests - Alternative command (both work identically)
• All standard pytest options are available (e.g., -v, -k, --no-cov)

Additional Setup

• .gitignore: Comprehensive Python gitignore including:
  • Testing artifacts (.pytest_cache/, coverage.xml, htmlcov/)
  • Claude settings (.claude/*)
  • Python build artifacts and virtual environments
  • Note: poetry.lock is NOT ignored and should be committed

Usage Instructions

1. Install dependencies:

   poetry install

2. Run all tests:

   poetry run test
   # or
   poetry run tests

3. Run specific tests:

   poetry run test tests/unit/
   poetry run test -k "test_name"
   poetry run test -m unit

4. Run tests without coverage:

   poetry run test --no-cov

5. View coverage report:

   • Terminal: Shown automatically after test run
   • HTML: Open htmlcov/index.html in browser
   • XML: Available at coverage.xml

Notes

• The coverage threshold is initially set to 0% to allow setup without existing tests
• Update --cov-fail-under in pyproject.toml to 80% once you have sufficient test coverage
• The validation test file (test_setup_validation.py) verifies that all testing infrastructure components are working correctly
• All chapter modules (ch2-ch8) are configured for coverage reporting
• The project is ready for immediate test development

Next Steps

1. Start writing unit tests in tests/unit/ directory
2. Add integration tests in tests/integration/ directory
3. Increase coverage threshold to 80% once tests are written
4. Consider adding additional testing tools as needed (e.g., pytest-asyncio for async code)