TIL: Dash Testing, Docker Compose, and Python Mocking

Web Development and Testing

Dash Framework Testing

• It is possible to memoize dash callback responses with flask-caching
• Dash supports response caching to improve performance
• Flask-caching integration allows for sophisticated caching strategies
• Important for optimizing callback-heavy Dash applications

Flask-Dash Integration Best Practices

• Always ensure that dash registration in a Flask-Dash app is configurable
• Might want to not load dash when testing backend only
• Separation of concerns between backend API and frontend visualization
• Enables more targeted testing strategies

Testing and Mocking

Python Mock Module Best Practices

• When mocking python functions in a flask test, ensure you reference the module where the function is called, not where it originates from
• Common pitfall: mocking at the wrong import level
• Mock at the point of use, not the point of definition
• Critical for effective unit testing in complex applications

Infrastructure and Networking

Docker Compose Development Insights

• docker-compose has no docstrings
• Interesting observation about code documentation practices
• Even popular tools can have documentation gaps
• Reminder of the importance of good code documentation

DNS and Network Tools

Pi-hole Architecture

• pihole’s Faster than light engine is a fork of dnsmasq
• Built on proven DNS server technology
• Optimized for ad-blocking and DNS filtering
• Demonstrates how open source projects build on each other

Command Line Tools

• argparse does support sub-commands
• Python’s built-in argument parsing library is more capable than often realized
• Enables building complex CLI interfaces with nested commands
• Alternative to third-party libraries like Click for simpler use cases