NUnit - Asserting Exception and properties

Question

Hi, I'd like to Assert that an exception is being thrown and then check some of the properties of the thrown exception.

I was under the impression that I could do something like the following:

ICommand command = CreateCommandObj();
Assert.That( () => command.DoWork(), Throws.TypeOf<ArgumentException>(),                        
                     Has.Property("ParamName").EqualTo("myParam") &
Has.Property("Message").EqualTo("myMessage") );

However this doesn't even compile and looking at the expected parameters for Assert.That I can't see how I would be able to do this? I'm sure I have used this before though...

Note the above is a contrived example to illustrate the point, ignore the fact I am looking for an ArgumentException on a method that doesnt except any parameters :)

Any help appreciated.

1) Cannot convert lambda expression to type 'object' because it is not a delegate type.

Answer 1

Try && - logical and versus bitwise and

Edit:

I think you're looking for Assert.Throws if you're using the constraint interface. Not sure how you would assert on message. I think the old style is clearer for what you're trying to accomplish:

  try
  {
    command.DoWork();
    Assert.Fail("ArgumentException Expected");
  }
  catch (ArgumentException e)
  {
    Assert.AreEqual("Expected Message", e.Message);
  }

Answer 2

Ok, sorted.

I need to use the following syntax:

ICommand command = CreateCommandObj();
Assert.That( () => command.DoWork(), 
                   Throws.TypeOf<ArgumentException>()
                   .And.Message.Equals("MyMessage"));

This approach allows me to check properties on the thrown exception. I can add any number of And or Or's to the Assert.

Thanks everyone for the suggestions.

Answer 3

You test for exceptions with the [ExpectedException] attribute on your method. e.g.

[Test] 
[ExpectedException(typeof(InvalidOperationException))]
public void Test_SomeMethod()
{
    something.SomeMehthod();
}

You can set the properties of the expected exception in the constructor of the ExpectedException attribute.

EDIT You could also specify your test attributes like the following:

[Test]
[ExpectedException(ExpectedException = typeof(InvalidOperationException), ExpectedMessage = "Somethings not right")]
public void Test_SomeMethond()
{
    something.SomeMehthod();
}