http://weblogs.asp.net/nunitaddin/archive/2008/12/02/testdriven-net-2-18-nunit-2-5-beta.aspx

Jamie covers off some of the new things in NUnit 2.5 which are pretty cool, but the one thing he omitted (and I think is quite awesome) is the Assert.Throws<T>(); assertion.

Previously (NUnit 2.4 and below) you would either have to use the [ExpectedException()] attribute or implement the exception handling logic yourself in your test. Issues with using the ExpectedException attribute are well known. I’m doing this without VS at hand, so forgive me if parts are wrong, but for example:

[Test]
[ExpectedException(typeof(ArgumentNullException))]
public void TestArgumentNullThrowsException()
{
    new MyObject(null);
}
  
  
[Test]
public void TestArgumentNullThrowsException()
{
  bool thrown = false;
  
  try
  {
    new MyObject(null);
  }
  catch (ArgumentNullException e)
  {
    // Check if the message is correct
    thrown = true;
  }
  catch (Exception e)
  {
    throw; // Any unexpected exceptions still get raised up
  }
  finally
  {
    Assert.IsTrue(thrown, "Expected exception should be thrown, but was not");
  }
}

Well with NUnit 2.5, you can lambda the entire thing and the testcase becomes so much simpler:

[Test]
public void TestArgumentNullExceptionIsThrown()
{
  Assert.Throws<ArgumentNullException>( () =>  new MyObject(null)  );
}

…And why is this good for TestDriven.NET? It means I can install NUnit 2.5 and actually use it with TD.NET, instead of using the GUI test runner.