Wikipedia Test Wiki

"The Wikipedia Test Wiki is for to test their code without breaking all of, and blowing the world up."

The Wikipedia Test Wiki may also be used in a classroom environment for  basic wiki editing to avoid the great confusion resulting from creating pages and breaking a regular project, although this may not always be desirable because of the occasional difference between the test interface and a typical Wikimedia project interface.

See also: test2.Wikipedia. (As of: 03 April 2013)
 * Wikipedia Test Wiki Interactive Statistics, from Wikistatistics.net