Testing, Design, and Architecture

Quality topics are ways to control change, not separate trivia buckets. Interviewers expect you to explain which behavior deserves tests, which abstraction lowers coupling, which principle prevents a specific failure mode, and when a pattern is heavier than the problem.

This group covers testing strategy and tooling, OOP and SOLID, clean code, design patterns, application and distributed architecture, messaging, and system design interviews. Strong answers tie each idea to a concrete codebase decision.

Checklist:

• Map tests to risk and feedback speed, not coverage vanity.
• Compare patterns and principles by trade-off, not slogan.
• Explain architecture choices with constraints and failure modes.
• Use child topics for testing, OOP, patterns, and architecture depth.