MbUnit has a Visual Studio Add-In using the NUnitAddIn framework. Setting the framework is done through the following steps:

1. Get the latest NUnitAddIn installed on your machine,
2. Copy the MbUnit binaries to the NUnitAddIn folder,
3. Edit the NUnitAddIn.config file as follows:

   <?xml version="1.0"?>
   <configuration>
     <nunitaddin>
       <frameworktestrunners>
         <testRunner name="MbUnit"
                        typeName="MbUnit.AddIn.MbUnitTestRunner" 
                        assemblyPath="MbUnit.AddIn.dll"  />
         <testRunner name="NUnit"
                        typeName="NUnitAddIn.NUnit.TestRunner.SimpleNUnitTestRunner" 
                        assemblyPath="NUnitAddIn.NUnit.dll"  />
         ...
       </frameworktestrunners>
     </nunitaddin>
   </configuration>

That's it. You can now right click on an assembly, namespace or fixture and execute it using "Run Tests...".