How do you decide what to test in your application?
Answer: Focus on testing: Critical business logic. Edge cases and boundary conditions. Public methods and APIs. Error handling and exception paths. Code that is prone to bugs or complex.
What interviewers expect
- A clear definition tied to Testing in Unit Testing projects
- Trade-offs (performance, maintainability, security, cost)
- When you would and would not use it in production
Real-world example
In a production Unit Testing application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.
How to explain in the interview
- Define the concept in one or two sentences.
- Context — where it fits in Unit Testing architecture.
- Example — a specific project, bug, or performance win.
- Trade-off — what you gain vs what you sacrifice.
Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.