A MbUnit fixtures have a default time out set to 10 minutes. Time outs are there to ensure that a test does not block the entire test process. For example, a test that pops up a dialog window requiring manual interaction would kill the entire test execution.

To change the time out of a fixture, simply specify the number of minutes in the fixture attribute constructor:

// A fixture with 10 minute timeout
[TestFixture(TimeOut = 10)]
public class MyFixture
{
   [Test]
   public void AMessageBoxShouldNotBlockTheTestProcess()
   {
       MessageBox.Show("I'm blocking the test automation");
   }
}