csUnit

csUnit is a free and open source unit testing tool for the .NET Framework. csUnit works with all .NET languages including C#, Visual Basic .NET, J#, and managed C++. It comes with a choice of command line, graphical user interface, and an addin for Visual Studio.
    *  Loads one or more test assemblies and displays the hierarchy of tests, implemented in those assemblies.
    * Runs all tests in a separate thread and a separate appdomen thus isolating the application from the code under test. The GUI stays responsive.
    * Finds test fixtures (classes containing tests) and tests based on attributes or based on naming conventiones. No common baseclass or interface implementation required.
    * Supports attributes based implementation of test fixtures. ([TestFixture], [SetUp], [TearDown], [SetUp], [Ignore("...")]).
    * Setup and TearDown attributes for fixture specific setup and teardown code.
    * TestAssemblyFixture with SetUp and TearDown for assembly specific setup and teardown code.
    * Categories for grouping tests. Each test fixture and test can be in multiple categories.
    * Tests can be written in any .NET language
    * Shadow copies all used assemblies. A new version of the test assembly can be built while tests are still running.
    * Displays count of executed tests, errors, failures, skipped tests, and assertions.
    * Displays amount of time needed to execute the configured tests.
    * Displays the location (file and linenumber) of each error and failure. This includes the call stack for easier debugging.
    * Displays skipped tests and the reason why they have been skipped.
    * Redirects Console.Error and Console.Out to a separate tab.
    * csUnit helps reducing test effort by displaying basic statistics about test cases such as absolute and relative time consumed. Times are measured using a high-resolution timer (100ns) for better accuracy.
    * csUnit 2.2 and later support parameterized tests with as many parameters as needed.

Go to http://www.csunit.org/

See also these related projects.