PHP extensions can test their userland (PHP) functionality using so called "phpt Tests". phpt Tests consist of several parts with their main part being regular PHP code to test PHP. On the website of the PHP Quality Assurance Team you can find a documentation of the phpt Tests syntax on the page Writing Tests, if your are interested in the details. Most extensions contain a tests/ subdirectory in the PHP source code to ship the tests together with C code of the extensions. So do ext/mysql and ext/mysqli.
They show the testing structure they used and some of the stats they found from their runs. The rest of the post is dedicated to how it was all set up:
- implemented as phpt Tests
- which need new settings
- Using run-tests.php to run the tests
- Failing tests
- Useful run-tests.php options and features
They also briefly mention what a typical set of test results are (for the time the post was made).