SQL Server 2005 | SQL Server 2008 | SQL Server 2008 R2
There is a new testing suite for BI solutions named BI.Quality available at codeplex: http://biquality.codeplex.com/. The suite is based on NUnit and supports quite a lot of different testing methods. What I like most is the ability to automatically compare result sets from different sources, for example SQL and MDX. This allows you to define test scenarios your system must meet after the OLAP cube has been loaded. Or think of migration projects where you can still run queries against the old system and compare the results with the new system. As everything can be automated, tests can be run on a regular basis (for example directly after every cube processing) to make sure, that all facts are really complete and correct.
Here are some screenshots:
More info can be found at http://biquality.codeplex.com/.
Disclaimer: Although it is an open source project the current development is done by ORAYLIS (my employer).