What is a primary limitation of code coverage as a testing measurement?

Code coverage is a metric that indicates the percentage of code that has been executed during testing. While it provides insights into how much of the codebase is being tested, it does not necessarily reflect whether all functionalities are tested effectively. This means that even with high code coverage percentages, some paths, conditions, or business logic may not be exercised during tests, potentially leaving certain features unverified in terms of their expected behavior. Thus, the presence of code coverage might give a false sense of security regarding the quality and reliability of the software.

In practice, achieving high code coverage does not guarantee that the application performs as intended when subjected to various conditions or inputs. Consequently, relying solely on code coverage as a measure of testing effectiveness can overlook crucial aspects of software functionality that must be validated through comprehensive testing methods, including end-to-end or user acceptance testing. This is why it is critical for testers and developers to complement code coverage metrics with other testing approaches that evaluate system behavior and ensure that functional requirements are met.