After a long period of absence, test.wikipedia.org has returned. Unlike the old test.wikipedia.org, it is running essentially the same code as the rest of the Wikimedia wikis. The difference is that it uses the copy from NFS rather than the synced copy on the local apache hard drives, which means that we can more easily test for errors in the Wikimedia environment before we take the final step and do a sync. Hopefully this will reduce the number of transient PHP errors seen on the site, which are most often due to differences between the developer's test environment and the Wikimedia environment.
The rather cynical protected warning on the main page is my doing, I want to have at least one goatse-free page on the wiki so that I can test the code in peace.
-- Tim Starling