Which statement correctly distinguishes unit, integration, and system testing?

Which statement correctly distinguishes unit, integration, and system testing?

• A. Unit tests validate the complete system end-to-end.
• B. Integration tests check individual components in isolation.
• C. System tests validate the complete system end-to-end.
• D. All three testing types serve the same purpose.

Answer: (C)

End-to-end validation of the entire, integrated product is what system testing focuses on. It exercises the complete system in a realistic environment to ensure all parts work together and that typical user workflows—from start to finish—behave as expected. This is what sets it apart from other levels: unit testing targets individual components in isolation, checking that a single function or module behaves correctly on its own; integration testing verifies how multiple components interact with each other, but not necessarily across the full user journey; and claiming that all three serve the same purpose ignores their different scopes and goals.

End-to-end validation of the entire, integrated product is what system testing focuses on. It exercises the complete system in a realistic environment to ensure all parts work together and that typical user workflows—from start to finish—behave as expected. This is what sets it apart from other levels: unit testing targets individual components in isolation, checking that a single function or module behaves correctly on its own; integration testing verifies how multiple components interact with each other, but not necessarily across the full user journey; and claiming that all three serve the same purpose ignores their different scopes and goals.