feat: set up comprehensive Python testing infrastructure

[llbbl]

Set up Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the Russian Cities Parser project, providing developers with a ready-to-use testing environment.

Changes Made

Package Management

• Set up Poetry as the primary package manager with pyproject.toml configuration
• Migrated dependencies from requirements.txt to Poetry (parselab, lxml)
• Added testing dependencies: pytest, pytest-cov, pytest-mock as development dependencies

Testing Configuration

• pytest configuration in pyproject.toml with:
  • Test discovery patterns for flexible test file naming
  • Coverage reporting with 80% threshold
  • HTML and XML coverage report generation
  • Custom markers: unit, integration, slow
  • Strict configuration for better test reliability

Directory Structure

• Created proper testing hierarchy:

  tests/
  ├── __init__.py
  ├── conftest.py
  ├── unit/
  │   └── __init__.py
  ├── integration/
  │   └── __init__.py
  └── test_infrastructure_validation.py
  

Shared Test Fixtures

• Comprehensive fixtures in conftest.py including:
  • Temporary directory and file fixtures
  • Mock environment variables
  • Sample data fixtures for Russian cities
  • Mock network responses for testing web scraping
  • Cache and network manager mocks

Development Tools

• Updated .gitignore with testing artifacts, build files, IDE files
• Validation tests to ensure infrastructure works correctly
• Coverage configuration excluding test files and virtual environments

Testing Infrastructure Features

Running Tests

# Install dependencies
poetry install

# Run all tests
poetry run pytest

# Run tests without coverage threshold failure
poetry run pytest --cov-fail-under=0

# Run only unit tests
poetry run pytest -m unit

# Run only integration tests  
poetry run pytest -m integration

Coverage Reporting

• Terminal output with missing line indicators
• HTML report generated in htmlcov/ directory
• XML report for CI/CD integration (coverage.xml)
• Configurable threshold (currently set to 80%)

Test Organization

• Unit tests: tests/unit/ for isolated component testing
• Integration tests: tests/integration/ for end-to-end testing
• Custom markers for categorizing and filtering tests
• Shared fixtures for common test scenarios

Validation

✅ All infrastructure validation tests pass (8/8)
✅ Coverage reports generate correctly (HTML + XML)
✅ Poetry dependency management works
✅ Test discovery and execution work as expected
✅ Fixtures are properly configured and accessible

Next Steps

Developers can now:

1. Write unit tests in tests/unit/ for individual functions and classes
2. Write integration tests in tests/integration/ for complete workflows
3. Use provided fixtures for common testing scenarios
4. Run tests with coverage to ensure code quality
5. Add custom markers for specific test categories

The infrastructure is ready for immediate use - just start writing tests!

🤖 Generated with Claude Code