feat: Set up comprehensive Python testing infrastructure

[llbbl]

Set up Python Testing Infrastructure

Summary

This PR establishes a comprehensive testing infrastructure for the XBlock-ETH project using Poetry as the package manager and pytest as the testing framework.

Changes Made

Package Management

• Added Poetry configuration in pyproject.toml with project metadata and dependencies
• Migrated dependencies from existing codebase (primarily requests for data downloading)
• Set up development dependencies: pytest, pytest-cov, pytest-mock

Testing Configuration

• Pytest configuration with test discovery patterns, coverage settings (75% threshold), and custom markers (unit, integration, slow)
• Coverage reporting in HTML, XML, and terminal formats with branch coverage enabled
• Test filtering and strict configuration for reliable test execution

Directory Structure

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

Shared Testing Fixtures

The conftest.py provides comprehensive fixtures for:

• Temporary directories for test file operations
• Mock objects for zipfiles, HTTP requests, and file operations
• Sample data for blocks and transactions
• Network isolation to prevent actual HTTP calls during testing
• Environment cleanup for consistent test runs

Updated Configuration

• Enhanced .gitignore with testing artifacts, Python cache files, virtual environments, and IDE files
• Validation tests to verify all components work correctly together

How to Run Tests

Install Dependencies

poetry install

Run All Tests

poetry run pytest

Run with Verbose Output

poetry run pytest -v

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 Report

poetry run pytest --cov-report=html
# Open htmlcov/index.html in browser

Validation

The infrastructure has been validated with 18 passing tests that verify:

• ✅ Python version compatibility (3.8+)
• ✅ All testing dependencies import correctly
• ✅ Custom test markers function properly
• ✅ Project structure is correct
• ✅ Shared fixtures work as expected
• ✅ Test discovery and execution work properly
• ✅ Coverage reporting generates successfully (77.90% coverage achieved)

Notes

• Poetry lock file is included in version control for reproducible builds
• Coverage threshold set to 75% for initial setup, can be increased as test suite grows
• Network calls blocked by default in tests to ensure fast, reliable execution
• Flexible fixture system allows easy extension for project-specific testing needs

The testing infrastructure is now ready for developers to start writing unit and integration tests for the blockchain data analysis functionality.