Which phase tests individual units of a software application?

Which phase tests individual units of a software application?

• A. Unit test
• B. System test
• C. Beta test
• D. Fuzz

Answer: (A)

Testing individual units of a software application is done with unit testing. It validates each small piece of code—like a function or a class—working correctly on its own, usually in isolation from the rest of the system. Developers use mocks or stubs for dependencies so the unit's behavior can be checked deterministically. This early, focused testing catches defects at the source and provides fast, repeatable feedback before components are integrated. In contrast, system testing examines the whole application together to verify end-to-end behavior; beta testing involves real users; fuzz testing feeds random or malformed inputs to find robustness issues rather than verify a single unit.

Testing individual units of a software application is done with unit testing. It validates each small piece of code—like a function or a class—working correctly on its own, usually in isolation from the rest of the system. Developers use mocks or stubs for dependencies so the unit's behavior can be checked deterministically. This early, focused testing catches defects at the source and provides fast, repeatable feedback before components are integrated. In contrast, system testing examines the whole application together to verify end-to-end behavior; beta testing involves real users; fuzz testing feeds random or malformed inputs to find robustness issues rather than verify a single unit.