Hi,
There are some tools out there, but if you really intend to do some tests you should investigate a bit more.
Testing is not that hard, it's just a question of reading, understanding and applying what you've learned.
Have a read about
Unit Testing and
Integration Testing, this should help. You should also take a look at
Test Driven Development
There is a great tool out there that just came out from Microsoft Labs:
Pex and Moles - Isolation and White box Unit Testing for .NET
So, testing is a concept, it is an art, there are no good tools that will do the work. Testing is part of any development life cycle thus it is something that has to be well thought and that demands efforts and time.
Hope it helps.