Which testing level focuses on validating each individual component in isolation before integration?

Which testing level focuses on validating each individual component in isolation before integration?

• A. Unit testing
• B. Integration testing
• C. System testing
• D. User acceptance testing

Answer: (A)

The main idea here is validating each smallest testable part on its own before anything is combined with others. Unit testing focuses on individual functions, methods, or components in isolation, using mocks or stubs to stand in for the rest of the system. By testing these pieces separately, you can confirm that each one behaves as intended, catch defects early, and make debugging and future changes easier. This level is the starting point in a typical testing sequence. After unit tests, integration testing checks how those pieces work together, system testing looks at the whole system’s behavior, and user acceptance testing verifies that the product meets user and business needs in real-world use.

The main idea here is validating each smallest testable part on its own before anything is combined with others. Unit testing focuses on individual functions, methods, or components in isolation, using mocks or stubs to stand in for the rest of the system. By testing these pieces separately, you can confirm that each one behaves as intended, catch defects early, and make debugging and future changes easier.

This level is the starting point in a typical testing sequence. After unit tests, integration testing checks how those pieces work together, system testing looks at the whole system’s behavior, and user acceptance testing verifies that the product meets user and business needs in real-world use.