[TazeTSchnitzel]

Looks like they've copied some of PHP's tests, yes. But being able to run run-tests.php and being compatible aren't quite the same thing, really. It's how many tests pass that count.

Technical side-note: /Zend there appears to be just the tests for the Zend engine (i.e. from PHP's /Zend/tests), while the containing directory contains test folders copied from other parts of PHP (like the standard library)

[Twirrim]

It's also worth noting that not even PHP itself passes their own test suite. At the time of writing http://gcov.php.net/viewer.php?version=PHP_5_5 states:

Overview of PHP_5_5

Build Status: OK Last Build Time: 2 days

Compile Warnings: 611 Code Coverage: 0.3% Test Failures: 78 Expected Test Failures: 42 Valgrind Reports: 44

The "Expected Test Failures" is fascinating. http://gcov.php.net/viewer.php?version=PHP_5_5&func=expected...

[TazeTSchnitzel]

That's true, but PHP still passes the vast majority of its tests.