feat: Set up comprehensive Python testing infrastructure with Poetry

[llbbl]

Set up Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the lightweight_mmm project using Poetry as the package manager and pytest as the testing framework.

Changes Made

Package Management

• Migrated to Poetry: Created pyproject.toml with complete project configuration
• Dependency migration: Transferred all dependencies from requirements.txt and setup.py to Poetry
• Development dependencies: Added pytest, pytest-cov, and pytest-mock as dev dependencies

Testing Configuration

• pytest configuration:
  • Set up test discovery patterns
  • Configured coverage reporting with 80% threshold
  • Added custom markers: unit, integration, and slow
  • Configured output formatting and strict options
• Coverage settings:
  • HTML and XML report generation
  • Exclusion patterns for non-production code
  • Branch coverage enabled

Directory Structure

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

Shared Fixtures (conftest.py)

• temp_dir: Temporary directory for test files
• mock_data: Synthetic MMM data for testing
• mock_config: Configuration dictionary
• sample_media_data: Sample media spend data
• sample_target_data: Sample sales data
• mock_model_params: Model parameters for testing
• reset_random_seed: Ensures reproducible tests
• capture_logs: Log capturing fixture

Development Commands

• poetry run test - Run all tests
• poetry run tests - Alternative command (both work)
• All standard pytest options are available

Running Tests

1. Install dependencies:

   poetry install

2. Run all tests:

   poetry run test

3. Run with specific markers:

   poetry run pytest -m unit  # Unit tests only
   poetry run pytest -m "not slow"  # Skip slow tests

4. Run with coverage report:

   poetry run pytest --cov-report=html

Notes

• The infrastructure is ready for developers to start writing tests immediately
• Coverage threshold is set to 80% to encourage comprehensive testing
• The validation test file (test_setup_validation.py) verifies the infrastructure works correctly
• Poetry lock file is NOT gitignored to ensure reproducible builds
• The existing test files in the lightweight_mmm package remain unchanged