Set up Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the validate_email Python project using Poetry for package management and pytest as the testing framework.

Changes Made

Package Management

• Poetry Configuration: Created pyproject.toml with complete project metadata migrated from setup.py
• Dependency Management: Added testing dependencies as development dependencies:
  • pytest (^8.0.0) - Core testing framework
  • pytest-cov (^5.0.0) - Coverage reporting
  • pytest-mock (^3.14.0) - Mocking utilities

Testing Configuration

• pytest Configuration:

  • Test discovery patterns for test_*.py and *_test.py files
  • Coverage reporting with 80% threshold requirement
  • Multiple report formats: terminal, HTML, and XML
  • Custom markers: unit, integration, and slow
  • Strict mode enabled with verbose output

• Coverage Configuration:

  • Source tracking for validate_email module
  • Exclusions for test files, virtual environments, and build artifacts
  • Precision reporting with line-level detail
  • Skip covered lines in terminal output for clarity

Directory Structure

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

Shared Fixtures (conftest.py)

• temp_dir: Temporary directory for test files
• mock_email_config: Mock email configuration data
• mock_dns_resolver: Mock DNS resolver for MX lookups
• mock_smtp_connection: Mock SMTP connection
• sample_mx_records: Sample MX record data
• network_timeout: Standard timeout value
• test_data_dir: Path to test data directory

Development Commands

• poetry run test - Run all tests
• poetry run tests - Alternative command (both work)
• Standard pytest options are available through these commands

Additional Updates

• Updated .gitignore with:
  • Testing artifacts (.pytest_cache/, .coverage, htmlcov/, etc.)
  • Poetry files (excluding poetry.lock from gitignore as recommended)
  • Claude settings (.claude/*)
  • Virtual environments, IDE files, and temporary files

How to Use

1. Install dependencies:

   poetry install

2. Run tests:

   poetry run test
   # or
   poetry run tests

3. Run specific test categories:

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

4. Generate coverage reports:

   • HTML report: htmlcov/index.html
   • XML report: coverage.xml
   • Terminal report: Automatically displayed

Notes

• The coverage threshold is set to 80% but won't be enforced until actual tests are written
• All infrastructure validation tests pass successfully
• The setup follows Python testing best practices with clear separation of concerns
• Poetry lock file is intentionally not gitignored to ensure reproducible builds