In the previous two posts I described how you can create unit tests for threaded code as well as how you can de-couple your tests from external errors on the internet.

In this post I’ll show how to use GCOV and CoverStory to ensure that you are actually testing all parts of your code. Or at least obtain knowledge about which parts of your code that are being tested and which parts that are not being tested by your unit tests.

Having a high degree of code coverage in your unit tests helps to ensure that your code will continue working as expected even after you change parts of it, e.g. when fixing bugs, re-factoring it, adding new features, etc.

The coverage data can also be used to show when you have added enough tests to your code. Once you have obtained full test coverage of a certain function, adding more tests for that same function will probably not help you find more bugs in the code. Instead you can now focus your efforts on adding new functionality without having to worry about it breaking behind your back.

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