Sammy Kaye Powers has posted the latest parts in his series looking at testing the PHP language with phpt tests. So far he's helped you compile PHP from source, run the test suite, learn about the phpt files and debug failing tests. He continues the series with two new posts:

• 05: Finding untested code
• 06: Submitting a PR to php-src

In the 5th part of his series he shows how to use the PHP gcov site to locate lines of code in the PHP language core that aren't tested yet, how to create a new test to cover it and generating a code coverage report to see how much you've tested. In Part 6 he shows you how to take what you've created and submit it back to the PHP project on GitHub as a Pull Request (no RFC needed) based on changes from your own forked repository.

When it comes to code coverage and untested parts of your application (unit tested, of course), Zoe Slattery has a suggestion that could make your life easier anyway - follow the core PHP developer's example:

But - there is another way, and as usual the PHP core developers are showing us the way. The fastest way to improve percentage of code covered is to REMOVE UNTESTED CODE! Accordingly we saw the test coverage of PHP 5.3 increase from about 55% to a little over 70% over the summer of 2008. At the same time the lines of code in PHP dropped by about 50KLOC. How can this be?

Removing untested code (that's not needed anyway) can reduce unit testing times dramatically and can help you keep your code clean, lean and simple for the upgrades that will come later on.