feat: Set up complete Python testing infrastructure with Poetry

[llbbl]

Python Testing Infrastructure Setup

Summary

This PR establishes a complete testing infrastructure for the Python project using Poetry as the package manager and pytest as the testing framework. The setup provides a ready-to-use testing environment with comprehensive fixtures, coverage reporting, and organized test structure.

Changes Made

Package Management

• ✅ Utilized existing Poetry configuration in pyproject.toml
• ✅ Added testing dependencies as dev dependencies:
  • pytest ^8.3.2 - Core testing framework
  • pytest-cov ^5.0.0 - Coverage reporting plugin
  • pytest-mock ^3.14.0 - Mocking utilities

Testing Configuration

Added comprehensive testing configuration to pyproject.toml:

pytest settings:

• Test discovery patterns for test_*.py and *_test.py files
• Custom markers: unit, integration, slow
• Strict configuration and markers enforcement
• Verbose output by default
• Test paths set to tests/ directory

Coverage settings:

• 80% coverage threshold requirement
• Multiple report formats: terminal, HTML (htmlcov/), XML (coverage.xml)
• Proper exclusions for test files, virtual environments, and build artifacts
• Branch coverage analysis enabled
• Intelligent line exclusions for pragma statements and abstract methods

Directory Structure

tests/
├── __init__.py
├── conftest.py                      # Shared fixtures and configuration
├── test_infrastructure_validation.py # Infrastructure validation tests
├── unit/                            # Unit tests directory
│   └── __init__.py
└── integration/                     # Integration tests directory
    └── __init__.py

Shared Fixtures (conftest.py)

Comprehensive set of reusable fixtures for common testing needs:

• temp_dir - Temporary directory creation and cleanup
• temp_file - Temporary file with sample content
• mock_config - Mock configuration dictionary with common settings
• mock_env_vars - Environment variable mocking
• mock_logger - Pre-configured mock logger with all standard methods
• sample_data - Sample data structures (users, products, nested data)
• mock_file_system - Creates mock directory structure with sample files
• mock_api_response - Mock HTTP response object
• mock_database_connection - Mock database connection with cursor
• capture_logs - Log capturing utility
• reset_singleton_instances - Automatic singleton reset between tests

Auto-configuration features:

• Automatic test marking based on directory location (unit/integration)
• Project root automatically added to Python path

Additional Files

.gitignore - Comprehensive Python gitignore including:

• Python artifacts (__pycache__/, *.pyc, *.egg-info/)
• Test artifacts (.pytest_cache/, .coverage, htmlcov/, coverage.xml)
• Virtual environments (venv/, .venv/, virtualenv/)
• IDE files (.vscode/, .idea/)
• Claude settings (.claude/)
• Database files, backups, and temporary files

README.md - Basic project documentation

Example source structure (src/) - Sample module to demonstrate coverage

Validation Tests

Created comprehensive validation suite (test_infrastructure_validation.py) that verifies:

• All testing dependencies are properly installed
• Directory structure is correctly created
• All fixtures work as expected (18 different fixtures tested)
• Custom markers are properly configured
• Coverage configuration is set up correctly
• Python path includes project root
• pytest-mock integration works

How to Use

Install Dependencies

poetry install --no-root

Run Tests

# Run all tests
poetry run pytest

# Run with verbose output
poetry run pytest -v

# Run without coverage
poetry run pytest --no-cov

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

# Run tests quietly
poetry run pytest -q

Run Tests by Category

# Run only unit tests
poetry run pytest -m unit

# Run only integration tests
poetry run pytest -m integration

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

Coverage Reports

# Run with coverage for source code
poetry run pytest --cov=src --cov-report=term-missing

# Generate HTML report
poetry run pytest --cov=src --cov-report=html
# Open htmlcov/index.html in browser

# Check coverage threshold
poetry run pytest --cov=src --cov-fail-under=80

Writing Tests

Example Test Structure

import pytest

class TestMyFeature:
    @pytest.mark.unit
    def test_basic_functionality(self):
        """Test basic feature functionality."""
        assert my_function(2, 3) == 5
    
    @pytest.mark.integration
    def test_with_external_service(self, mock_api_response):
        """Test integration with external service."""
        service = MyService()
        service.client = mock_api_response
        assert service.fetch_data() == {"status": "success", "data": []}
    
    def test_with_temp_files(self, mock_file_system):
        """Test file operations using mock file system."""
        assert (mock_file_system["data"] / "data.json").exists()
        data = process_file(mock_file_system["data"] / "data.json")
        assert data == {"test": "data"}

Validation Results

✅ All 18 validation tests pass successfully:

• Infrastructure setup validation
• Fixture functionality tests
• Directory structure verification
• Configuration validation
• Mock utilities verification

Notes for Developers

• The testing infrastructure is ready for immediate use
• Add your source code tests in the appropriate directories (unit/ or integration/)
• Use the provided fixtures to avoid boilerplate code
• Coverage is optional and configured to run with --cov flag
• Poetry scripts are configured but optional (can use poetry run pytest directly)
• When adding source code, coverage will automatically track it based on configuration

Configuration Choices

• Poetry was used as it was already configured in the project
• Coverage source is configured for common directories (src, app, lib) to avoid warnings
• Package mode is disabled in Poetry since this is for testing infrastructure only
• Markers are pre-configured but also auto-applied based on test location
• Fixtures cover the most common testing scenarios to maximize reusability

Dependencies Added

• pytest ^8.3.2: Main testing framework
• pytest-cov ^5.0.0: Coverage reporting integration
• pytest-mock ^3.14.0: Enhanced mocking capabilities

All dependencies are specified with compatible version ranges to ensure stability while allowing minor updates.