Currently, we've got a dedicated sqlite testbot ready for on-demand core testing. However, we need to be able to pass the 'confirmation' stage before it can be used. (Disclaimer: Some of the corners cut to make this actually work are, to be blunt, ugly!)
Unfortunately, the confirmation test fails due to simpletest failing the NonDefaultBlockAdmin test with a 'failed to find test tables to drop' test failure. I suspect this is a problem within simpletest & run-tests.sh, and not PIFR directly.
Looking at the server after the test runs, it almost appears that the simpletest tables are being created in a seperate sqlite database file, which may explain the 'failed to drop' error (i.e. the aren't in the site db to be dropped).
We could use:
1) Independent verification whether this is repeatable through UI based testing on an sqlite-based installation
2) A volunteer to build up a vagrant testbot (I can provide details on how to convert it to sqlite), and troubleshoot what's actually going on here. Start with https://drupal.org/node/2144475
3) A patch to drush which will enable 'drush si' to be passed a db_url parameter relative to the server root, instead of directory in which it was executed (which will get rid of the worst of the PIFR workarounds).