Question

Is there a way to specify that you want an NUnit test to fail, meaning that a fail should be reported as a pass and a pass should be reported as a fail? This would be useful when testing your own NUnit extensions. Here is an example of something I would like to be able to do:

[Test]
[ExpectFail]
public void TypeOf_fail() {
    string str = "abc";
    str.Should().Be.TypeOf<int>();
}

This does not compile because [ExpectFail] is an imaginary attribute to illustrate what I want to do, but the code inside the method works fine. This problem is specific to testing an NUnit extension in that you can normally just easily write your tests to pass, not fail. In this case you need prove that it is possible to write a failing test using the NUnit extension that you are testing.

Answer 1

What about Assert.Throws<XXXException>(x.DoSomething());

The nice thing here is that if the test passes (i.e. the exception was thrown), the return value is the actual exception itself, and you can then interrogate it and Assert further based on that..

Given that in this case you’re wanting to test NUnit extensions, which, I’m assuming, function by making Assert calls, you could Assert.Throws<AssertionException>(…), and then do the above.

I’m thinking of writing some similar test plumbing code which I might in turn need tests for, so I’ll let you know if I discover anything else in this area.