Generating Test Coverage Reports

Having tests in place, we should somehow measure what's tested and what isn't and strive to improve the situation. It's best to use automated tools that will collect and report this information.

Adding tests to such a small solution isn't incredibly challenging. The real difficulty comes with slightly more advanced and longer programs. Over the years, we have found that as we approach over 1,000 lines of code, it slowly becomes hard to track which lines and branches are executed during tests and which aren't. After crossing 3,000 lines, it is nearly impossible. Most professional applications will have much more code than that.

Code coverage report

To deal with this problem, we can use a utility to understand which code lines are "covered" by test cases. Such code coverage tools hook up to the SUT and gather the information on the execution of each line during tests to present it in a convenient report like the one shown here: