The current version of run-tests.php is a PHP 4 scripts which has grown over the years. We currently have about 8000 tests in PHP and running them sequentially using the existing script is beginning to take an unacceptably long time, the problem will only get worse as we add more tests. We prototyped parallel test execution a while ago and found that it could be done but it was impossibly difficult to do using the existing run-tests.php script. There are other improvements that we'd like to add to run-tests (for example XML output) which we thought would also be easier if the existing run-tests.php script was re-engineered. Over the past few months we have been working on this and have a prototype OO version of run-tests that is currently able to run most of the tests in ex/standard/tests. The code is designed so that adding parallel running will be easy, we'd like to propose that a student takes on (at least) this part of the work - it's interesting and quite difficult PHP coding. A good student could extend beyond this and implement other new features (XML, reporting).
Actively being worked on.