feat: Add comprehensive Python testing infrastructure with Poetry

[llbbl]

Add Comprehensive Python Testing Infrastructure

Summary

This PR sets up a complete testing infrastructure for the FSDP optimizers project, providing a ready-to-use testing environment for developers.

Changes Made

Package Management

• Added Poetry configuration in pyproject.toml with complete project metadata
• Migrated dependencies from setup.py to Poetry format
• Fixed module imports to use relative imports for proper package structure

Testing Framework Setup

• Added testing dependencies: pytest, pytest-cov, pytest-mock
• Configured pytest in pyproject.toml with:
  • Test discovery patterns for automatic test detection
  • Coverage reporting with 80% threshold requirement
  • HTML and XML coverage report generation
  • Custom markers: unit, integration, slow
  • Strict configuration for robust testing

Directory Structure

Created complete testing directory structure:

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

Testing Configuration

• Coverage configuration with source inclusion/exclusion rules
• Shared fixtures in conftest.py including:
  • temp_dir: Temporary directory management
  • mock_config: Mock configuration objects
  • sample_tensor: Sample PyTorch tensors
  • sample_model: Simple neural network models
  • optimizer_params: Standard optimizer parameters
  • random_seed: Reproducible random state
  • mock_fsdp_model: Mock FSDP models

Infrastructure Improvements

• Updated .gitignore with comprehensive Python exclusions
• Fixed import issues in optimizer modules (kron.py, kron_mars.py, muon.py, soap.py)
• Added validation tests to verify the setup works correctly

Running Tests

Install Dependencies

poetry install

Run All Tests

poetry run pytest

Run Tests by Category

# Unit tests only
poetry run pytest -m unit

# Integration tests only  
poetry run pytest -m integration

# Exclude slow tests
poetry run pytest -m "not slow"

Coverage Reports

# Terminal coverage report
poetry run pytest --cov-report=term-missing

# Generate HTML coverage report
poetry run pytest --cov-report=html

Validation

The setup includes validation tests that verify:

• ✅ All optimizer classes can be imported
• ✅ PyTorch and NumPy are available
• ✅ Pytest fixtures work correctly
• ✅ Test markers function properly
• ✅ Coverage reporting generates correctly

Notes

• Poetry lock file: poetry.lock is tracked in git for reproducible builds
• Coverage threshold: Set to 80% - can be adjusted in pyproject.toml
• Test structure: Ready for developers to add unit and integration tests
• Fixtures: Comprehensive shared fixtures available for consistent testing

This infrastructure provides a solid foundation for test-driven development and maintains high code quality standards.