feat: Set up complete Python testing infrastructure with Poetry

[llbbl]

Add Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the GPT-2 PyTorch implementation 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
• Dependency Migration: Migrated existing dependencies from requirements.txt and added missing ones (PyTorch, tqdm)
• Development Dependencies: Added pytest, pytest-cov, and pytest-mock as dev dependencies

Testing Configuration

• pytest Configuration:

  • Test discovery patterns for test_*.py and *_test.py files
  • Coverage reporting with 80% threshold requirement
  • HTML and XML coverage report generation
  • Custom markers: unit, integration, and slow

• Coverage Settings:

  • Source coverage focused on GPT2 module
  • Exclusions for test files and virtual environments
  • Detailed reporting with missing line numbers

Project Structure

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

Fixtures and Utilities

Created comprehensive fixtures in conftest.py:

• temp_dir: Temporary directory management
• mock_config: GPT-2 configuration mocking
• sample_text: Test text data
• mock_model_files: Mock model file creation
• mock_checkpoint_path: Checkpoint file simulation
• capture_stdout: Output capture for testing
• cleanup_cache: Automatic cache cleanup

Additional Updates

• Updated .gitignore: Added entries for:
  • Testing artifacts (.pytest_cache/, coverage.xml, htmlcov/)
  • Claude-specific files (.claude/*)
  • Python build artifacts and virtual environments
  • Note to preserve poetry.lock file

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 test

# Alternative command (both work)
poetry run tests

# Run specific test markers
poetry run pytest -m unit        # Unit tests only
poetry run pytest -m integration # Integration tests only
poetry run pytest -m "not slow"  # Skip slow tests

# Run with custom pytest options
poetry run pytest -v --tb=short  # Verbose with short traceback

Coverage Reports

• Terminal: Coverage summary shown after each test run
• HTML Report: Generated in htmlcov/ directory
• XML Report: Generated as coverage.xml for CI integration

Notes

• The 80% coverage threshold is configured but will fail initially since only validation tests are included
• Poetry was chosen as the package manager for its modern dependency resolution and lock file management
• All testing dependencies are isolated in the dev group to keep production dependencies clean
• The infrastructure is ready for immediate test development

Next Steps

Developers can now:

1. Write unit tests in tests/unit/
2. Write integration tests in tests/integration/
3. Use the provided fixtures for common testing scenarios
4. Run tests with coverage to ensure code quality