nUnit Assert.Throws TestCase attribute

Question

I have a test method like this:

[TestCase(16486, "BobBank2.site16486.1", "16486.1")]
[TestCase(16441, "BobBank2.site16441.1", "16441.1")]
[TestCase(16443, "BobBank2.site16443.1", "16443.1")]
public async Task CheckUserAccountLinkStatusTest(int providerId, string username, string userKey)

I need to make sure that the first case (16486) throws an error, always. Is it possible to modify the TestCase attribute to do this?

Answer 1

You could check

if(providerId==16486)
{
    Assert.Throws(...
}

but it would be better to have two separate tests, one that checks for the exception when it is expected and one that asserts that there is no exception when there shouldn't be.

Answer 2

While the @Connel.O'Donnell solution works, I'd suggest to:

1. Avoid conditional logic in unit tests.
   • By having if-statements in your unit tests, it's easier to have a bug.
   • It's more difficult to read and maintain the test with the logic branched.
   • Here is the Stack Overflow topic: Why should you avoid conditional logic in unit tests and how?
2. Separate tests that throws exception from those which doesn't throw one.

So, your new, separated test for asserting exception should more or less look like:

[TestCase(16486, "BobBank2.site16486.1", "16486.1")]
public async Task CheckUserAccountLinkStatusTest_ThrowsException(int providerId, string username, string userKey)
{
    // ...
    Assert.That(() => { /* ... */  }, Throws.Exception);
}