Which of the following testing types is best suited for verifying whether individual units of source code work as intended?

Unit Testing is a type of software testing where individual units or components of the software are tested in isolation. The purpose is to validate that each unit of the software performs as designed. A unit typically refers to the smallest piece of code that can be logically isolated in a system, such as a function, method, or class. Unit Testing is usually automated and is one of the first tests conducted during the software development lifecycle, often by developers. Unit Testing helps catch errors early in the development process, which can save time and resources later in the SDLC. Because each unit is tested separately, issues can be pinpointed to specific sections of code, which makes debugging more manageable. Why Other Options Are Wrong: A) Integration Testing: This verifies that multiple units or components work together as expected. It focuses on interactions between integrated units, not individual units. B) Regression Testing: This ensures that changes or updates to the software do not introduce new bugs. Regression tests cover broader parts of the application, not just isolated units. D) User Acceptance Testing (UAT): UAT is conducted to confirm whether the software meets the user’s requirements and works in real-world scenarios. It is a high-level test done at the end of the testing cycle. E) Stress Testing: Stress Testing examines how the software performs under extreme or unfavorable conditions. It is not concerned with individual units but rather the overall stability of the system under stress.