There are test hooks inside SQL Server that the product group can use.
There are plenty of blog posts out there describing how to do it yourself using a hex editor - Google for me and XVI32 and you'll find one.
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005