What does Code Coverage show?

Code Coverage measures the percentage of your code that is executed or "exercised" during testing. This metric is essential for understanding how much of your software is being tested and helps identify untested parts of the codebase. When tests run, they execute specific paths through the code, and Code Coverage tools provide insights into which lines, branches, and functions were actually invoked during the tests.

By focusing on Code Coverage, teams can recognize gaps in their testing efforts, ultimately leading to improvements in test quality and uncovering potential bugs or issues. A high Code Coverage percentage can indicate thorough test coverage, but it's essential to remember that it does not guarantee the absence of defects; it merely highlights the parts of the code that have been tested.

The other options provide different concepts that are not directly related to what Code Coverage measures. Overall performance of the application involves various metrics that assess system efficiency and user experience rather than testing depth. Code that has been written but not tested pertains to untested areas, while documentation of code functionality involves explaining what the code does rather than measuring its execution during tests.