feat: Set up comprehensive Python testing infrastructure

[llbbl]

Set up comprehensive Python testing infrastructure

Summary

This PR establishes a complete testing infrastructure for the PDF Compressor project, migrating from a simple requirements.txt setup to a professional Poetry-based development environment with comprehensive testing capabilities.

Changes Made

• Package Management Migration: Migrated from requirements.txt to Poetry with pyproject.toml configuration
• Testing Dependencies: Added pytest, pytest-cov, and pytest-mock as development dependencies
• Test Configuration: Configured pytest with comprehensive settings including:
  • 80% coverage threshold requirement
  • HTML and XML coverage report generation
  • Custom markers for unit, integration, and slow tests
  • Strict configuration and verbose output
• Directory Structure: Created organized test directory structure:

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

• Shared Fixtures: Created comprehensive conftest.py with reusable test fixtures:
  • temp_dir: Temporary directory for test files
  • sample_pdf_path: Mock PDF files for testing
  • mock_qapplication: PyQt application mocking
  • mock_subprocess: Subprocess command mocking
  • compression_test_data: Test data for compression operations
• Validation Tests: Added complete test suite to validate infrastructure setup
• Environment Configuration: Updated .gitignore with testing-related entries and IDE configurations

Testing Infrastructure Components

1. pytest Configuration (pyproject.toml):

   • Test discovery patterns
   • Coverage settings with 80% threshold
   • HTML and XML report generation
   • Custom test markers

2. Coverage Configuration:

   • Source directory inclusion (src/)
   • Exclusion of test files and common patterns
   • Multiple report formats (HTML, XML, terminal)

3. Shared Test Fixtures (tests/conftest.py):

   • File system mocking and temporary directories
   • PyQt widget mocking for GUI testing
   • Sample configuration data
   • Compression test data sets

Running Tests

After this setup, developers can run tests using:

# Install dependencies
poetry install

# Run all tests
poetry run pytest

# Run with coverage
poetry run pytest --cov=src

# Run specific test types
poetry run pytest -m unit          # Unit tests only
poetry run pytest -m integration   # Integration tests only
poetry run pytest -m slow          # Slow tests only

# Generate coverage reports
poetry run pytest --cov=src --cov-report=html

Coverage Reports

The setup generates coverage reports in multiple formats:

• HTML: htmlcov/index.html - Interactive coverage report
• XML: coverage.xml - For CI/CD integration
• Terminal: Summary displayed after test runs

Dependencies Migration

Before: requirements.txt

PyQt6
humanize

After: pyproject.toml with Poetry

• Production dependencies: PyQt6, humanize
• Test dependencies: pytest, pytest-cov, pytest-mock

Next Steps

This infrastructure is ready for developers to:

1. Write unit tests for the PDF compression logic
2. Create integration tests for the full application workflow
3. Add GUI tests for the PyQt interface
4. Integrate with CI/CD pipelines using the coverage reports

The validation tests confirm that all fixtures, markers, and coverage reporting work correctly. The setup follows Python testing best practices and provides a solid foundation for comprehensive test coverage.