I\'m looking to introduce a unit testing framework into the mix at my job. We\'re using Visual Studio 2005 (though we may be moving to 2008 within the next six months) and
We've been using xUnit.net. It seems to combine all the best of NUnit, MbUnit, and MSTest.
VSTT 2010 (Visual Studio Team System Test) should be a good bet if you are looking for functional test automation. Web services testing, UI testing, BizTalk testing and data-driven testing support. Please look at VSTT.
When I started unit testing, I started with NUnit as it is simple to set up and use. Currently I am using the built-in test runner that comes with ReSharper. That way, I can easily flip between code and test results.
Incidentally, NUnit detects when you have compiled your code, so you do not need to do any refresh in NUnit. ReSharper automatically does a build when you choose to run a specific test.
MbUnit is worth a look. It has a set of features comparable to NUnit. It has its own GUI, or can be integrated into Visual Studio if you have ReSharper. I would also recommend Rhino Mocks if you are doing any sort of TDD.