There were many things that were not working properly in the automated tests. For one thing, the integration tests contained in lib/test/importer and lib/test/wikiparser were not invoked at all!
Also, if I ran the tests from lib/test, none of the tests got run at all, on account of the fact that I wasn't set up properly to run Selenium tests (as I suspect many folks will be).
So, I did two things.
First, I annotated all the tests cases with @group=(unit|integration|gui). That way, I can run all the tests save the GUI ones, by writing:
phpunit -exclude-group gui .
If you create new TestCase classes, make sure you annotate them accordingly.
Second, I fixed the test harness for lib/test, so that it works exactly the same way as the harness for lib/test/core. That way, you can create a new TestCase simply by creating a file whose name ends with Test.php, and defining in it a class of the same name. No need for all those AllTests.php files anymore.
I have started migrating tests from lib/test/importer and lib/test/wikiparser to this new harness (those tests weren't working even with the old harness). I was able to do it for wikiparser tests (which are now under lib/test/TikiLib/WikiParser) but haven't had time to do the ones in lib/test/importer.
The testing infrastructure is described here.