feat: Set up comprehensive Python testing infrastructure

[llbbl]

Set up comprehensive Python testing infrastructure

Summary

This PR establishes a complete testing infrastructure for the Python Functions Programming Exercises project, providing developers with a ready-to-use environment for writing and running tests.

Changes Made

Package Management

• ✅ Poetry Setup: Added pyproject.toml with Poetry configuration as the package manager
• ✅ Dependencies: Added essential testing dependencies as dev dependencies:
  • pytest (v7.4.0+) - Main testing framework
  • pytest-cov (v4.1.0+) - Coverage reporting
  • pytest-mock (v3.11.0+) - Mocking utilities

Testing Configuration

• ✅ Pytest Configuration: Comprehensive pytest setup in pyproject.toml:
  • Test discovery patterns for various file naming conventions
  • Coverage settings with 80% threshold requirement
  • HTML and XML coverage report generation
  • Strict marker and config enforcement
  • Custom markers: unit, integration, slow, it (LearnPack compatibility)

Directory Structure

• ✅ Test Organization: Created proper testing directory hierarchy:

  tests/
  ├── __init__.py
  ├── conftest.py          # Shared fixtures and configuration
  ├── unit/
  │   └── __init__.py
  ├── integration/
  │   └── __init__.py
  └── test_infrastructure.py  # Validation tests
  

Shared Testing Utilities

• ✅ Comprehensive Fixtures in tests/conftest.py:
  • temp_dir - Temporary directory management
  • mock_config - Configuration mocking
  • app - Dynamic exercise module loading
  • mock_print / mock_input - Built-in function mocking
  • capture_stdout - Output capture utilities
  • sample_data - Common test data structures
  • mock_file_system - File system mocking
  • environment_vars - Environment variable mocking

Development Workflow

• ✅ Git Integration: Updated .gitignore with testing exclusions:
  • Coverage files (.coverage, htmlcov/, coverage.xml)
  • Test caches (.pytest_cache/)
  • Virtual environments and IDE files
  • Note: poetry.lock is tracked (not ignored) as per best practices

Validation & Quality

• ✅ Infrastructure Tests: Added comprehensive validation tests to ensure:
  • All fixtures work correctly
  • Directory structure is proper
  • Project compatibility is maintained
  • Testing utilities function as expected

How to Run Tests

Install Dependencies

poetry install

Run All Tests

poetry run pytest                    # All tests
poetry run python -m pytest         # Alternative command

Run Specific Test Categories

poetry run pytest -m unit          # Unit tests only
poetry run pytest -m integration   # Integration tests only
poetry run pytest -m slow          # Slow tests only

Run With Coverage

poetry run pytest --cov=exercises  # With coverage (default)
poetry run pytest --no-cov         # Without coverage

Generate Coverage Reports

poetry run pytest                   # Generates HTML (htmlcov/) and XML reports

Testing Features

• Coverage Reporting: 80% threshold with detailed HTML and XML reports
• Flexible Test Discovery: Supports multiple naming conventions
• Mocking Utilities: Built-in fixtures for common mocking scenarios
• Exercise Compatibility: Dynamic module loading for exercise-based testing
• Performance Testing: Support for slow test markers
• LearnPack Integration: Compatible with existing @pytest.mark.it markers

Notes

• No Unit Tests Written: This PR focuses solely on infrastructure setup, not writing actual tests for the codebase
• Backward Compatibility: Existing exercise tests should continue to work (with updated fixtures)
• Ready for Development: Developers can immediately start writing tests using the provided fixtures and configuration
• Lock File Management: poetry.lock is tracked in version control for reproducible builds

Validation

All validation tests pass, confirming:

• ✅ Testing infrastructure works correctly
• ✅ Fixtures and utilities are functional
• ✅ Coverage reporting generates properly
• ✅ Project structure is maintained
• ✅ Dependencies install successfully