feat: Set up comprehensive Python testing infrastructure

[llbbl]

Set up Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the QR Redactor Python project, migrating from a simple requirements.txt setup to a modern Poetry-based development environment with full testing capabilities.

Changes Made

Package Management

• ✅ Poetry Setup: Created pyproject.toml with Poetry configuration
• ✅ Dependency Migration: Migrated all dependencies from requirements.txt to Poetry format
• ✅ Test Dependencies: Added pytest, pytest-cov, pytest-mock, and pytest-asyncio

Testing Configuration

• ✅ Pytest Configuration: Comprehensive pytest settings in pyproject.toml

  • Custom markers: unit, integration, slow
  • Coverage reporting with 80% threshold
  • HTML and XML coverage output formats
  • Strict mode and enhanced output options

• ✅ Coverage Configuration: Detailed coverage settings

  • Source directory inclusion/exclusion rules
  • Multiple output formats (terminal, HTML, XML)
  • Skip lines for common non-testable code patterns

Directory Structure

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

Shared Test Fixtures

The conftest.py file provides comprehensive fixtures including:

• temp_dir and temp_file for file system testing
• sample_text and sample_sensitive_data for application-specific testing
• test_client for FastAPI endpoint testing
• test_db for isolated database testing
• mock_* fixtures for various mocking scenarios
• Environment variable mocking support

Development Workflow

• ✅ Testing Commands:

  • poetry run pytest - Run all tests
  • 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

• ✅ Coverage Reporting:

  • Terminal output with missing lines
  • HTML reports in htmlcov/ directory
  • XML reports for CI integration

Project Configuration

• ✅ Updated .gitignore: Added testing artifacts, coverage reports, and Claude settings
• ✅ Lock File Management: Poetry.lock properly tracked (not gitignored)

Validation

The infrastructure has been validated with a comprehensive test suite (test_infrastructure.py) that verifies:

• ✅ Pytest functionality and custom markers
• ✅ Fixture availability and functionality
• ✅ Mocking capabilities
• ✅ FastAPI test client integration
• ✅ Database fixture setup
• ✅ Async test support
• ✅ Project structure integrity
• ✅ Coverage configuration

Testing Instructions

Install Dependencies

cd qr-redactor
poetry install

Run All Tests

poetry run pytest

Run Tests with Coverage

poetry run pytest --cov=app --cov-report=html

Run Specific Test Types

# Unit tests only
poetry run pytest -m unit

# Integration tests only  
poetry run pytest -m integration

# Skip slow tests
poetry run pytest -m "not slow"

View Coverage Report

After running tests with coverage, open htmlcov/index.html in your browser.

Notes

• Poetry Lock File: The poetry.lock file is intentionally tracked in git for reproducible builds
• Coverage Threshold: Set to 80% - tests will fail if coverage drops below this threshold
• Test Database: Uses isolated SQLite database for testing that's automatically cleaned up
• FastAPI Integration: Full test client setup for API endpoint testing
• Async Support: Configured for testing async FastAPI endpoints

Ready for Development

The testing infrastructure is now ready for developers to start writing:

• Unit tests in tests/unit/
• Integration tests in tests/integration/
• All shared fixtures are available via conftest.py
• Coverage reporting will track test effectiveness
• CI/CD integration ready with XML coverage reports