What does 'code coverage' indicate in testing?

Code coverage is a critical metric in software testing that measures the extent to which the source code of a program is tested by automated tests. It specifically quantifies the percentage of code that has been executed during testing processes, providing insight into which portions of the codebase are covered by tests. This is important because it helps ensure that sufficient parts of the code are verified for correctness, reducing the risk of bugs and increasing software reliability.

High code coverage generally indicates that more tests have been conducted, which suggests a more thorough examination of the application. However, it's important to note that code coverage alone does not guarantee the absence of defects; it simply demonstrates the amount of code that has been run during testing.

In contrast, the other options do not accurately reflect the concept of code coverage. The total number of lines of code and the amount of code written by developers are related to size and complexity, not testing effectiveness. Additionally, the duration of testing activities pertains to the time spent on testing rather than the extent of code verification. Hence, the correct answer clarifies the specific focus of code coverage in relation to testing practices.