In a large application, which code branches are more important to be tested and how do you decide?

In a large application, prioritize testing for code branches that are critical to business operations, security, or user experience. This includes:

• Core Business Logic: Features directly impacting revenue, user accounts, or essential services.
• Security-Sensitive Paths: Authentication, authorization, payment processing, and data encryption/decryption.
• Error Handling and Edge Cases: Branches that manage unexpected inputs, system failures, or recovery scenarios, as these often reveal vulnerabilities or usability issues.
• Frequently Used or High-Traffic Areas: Code that is executed often is more likely to encounter defects.

Decisions are based on risk assessment: the potential impact of a failure (financial loss, data breach, reputational damage) and the likelihood of a branch being executed or encountering an error.