feat: Set up Python testing infrastructure with Poetry and pytest

[llbbl]

Set Up Python Testing Infrastructure

Summary

This PR establishes a complete testing infrastructure for the DNSChef project, migrating from Pipenv to Poetry for modern dependency management and setting up pytest as the testing framework.

Changes Made

Package Management

• Migrated to Poetry: Created pyproject.toml with Poetry configuration
• Preserved existing dependencies: Migrated dnslib from requirements.txt
• Maintained compatibility: Kept existing Pipfile for backward compatibility

Testing Dependencies

Added the following development dependencies:

• pytest (^7.4.0) - Core testing framework
• pytest-cov (^4.1.0) - Coverage reporting
• pytest-mock (^3.11.0) - Mocking utilities

Testing Configuration

Configured comprehensive pytest settings in pyproject.toml:

• Test discovery: Configured patterns for finding test files
• Coverage settings:
  • 80% coverage threshold
  • HTML and XML report generation
  • Branch coverage enabled
  • Excluded non-source files from coverage
• Custom markers: Added unit, integration, and slow test markers
• Strict mode: Enabled strict markers and configuration

Directory Structure

Created organized testing structure:

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

Shared Fixtures (conftest.py)

Created comprehensive fixtures for common testing needs:

• temp_dir and temp_file - Temporary file handling
• mock_config - DNS server configuration mocking
• mock_dns_query - DNS query object mocking
• mock_socket - Network socket mocking
• mock_logger - Logging mocking
• dns_server_config - Sample configurations
• sample_dns_records - Test DNS records
• reset_environment - Environment cleanup
• capture_stdout - Output capturing
• mock_args - Command-line argument mocking

Development Workflow

Updated .gitignore with:

• Testing artifacts (.pytest_cache/, .coverage, htmlcov/, etc.)
• Claude settings (.claude/*)
• Virtual environments
• IDE files
• Build artifacts
• Note: poetry.lock is intentionally gitignored as this is a tool, not an application

Validation

Created test_setup_validation.py to verify:

• All testing dependencies are properly installed
• Fixtures are available and functional
• Custom markers work correctly
• The main module can be imported
• Coverage tracking is enabled

How to Use

Install Dependencies

poetry install

Run Tests

You can use either command:

poetry run test
poetry run tests

Run Specific Tests

poetry run pytest tests/unit/
poetry run pytest -m unit
poetry run pytest -m "not slow"

Generate Coverage Reports

Tests automatically generate coverage reports:

• Terminal output with missing lines
• HTML report in htmlcov/ directory
• XML report as coverage.xml

Notes

• The project requires Python 3.7+ due to testing dependency requirements
• Coverage threshold is set to 80% - tests will fail if coverage drops below this
• The infrastructure is ready for developers to start writing actual unit and integration tests
• No actual unit tests for the codebase were written - only infrastructure setup and validation

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