Which of the following stages is NOT part of the test levels?

The correct choice is the stage labeled "Design Testing," which is not recognized as an official test level within the established software testing hierarchy. The recognized test levels typically include Component (or Unit) Testing, Integration Testing, and System Testing.

Component (Unit) Testing focuses on testing individual parts or components of the software to ensure that they function correctly in isolation. This is the first level of testing, where the aim is to validate the smallest testable parts of the application, often referred to as units.

Integration Testing follows, where multiple components or systems are combined and tested as a group. This stage is crucial for identifying interface defects between integrated units, ensuring that components work together as designed.

System Testing occurs after integration testing and involves testing the complete and fully integrated software product. This level of testing checks the system’s compliance with the specified requirements and ensures that end-to-end scenarios work as expected.

In contrast, "Design Testing," while it may refer informally to the examination of design specifications or design reviews, is not categorized as a formal test level like the others mentioned. Instead, it typically falls under activities conducted during the development process rather than being a separate stage of testing itself. Therefore, this distinguishes it clearly from the structured framework of formal testing levels