MSTest custom attributes

Question

Hello,

I'm trying to implement custom attributes to methods decorated with MSTest attributes.

Example: I need to catch unhandled exceptions in [AssemblyInitialize], [AssemblyCleanup],[TestInitialize], [TestCleanup]... methods. I've tried Fody, but it not works in this environment and any of my attribute class methods isn't called (Init(), OnEntry(), OnException()...).

In case of [TestMethod] I succesfully created my attribute which is derived from TestMethodAttribute and I overrided Execute() method. However, attributes like [AssemblyInitialize] are sealed.

Is there any solution based on attributes?

Thank you!

Answer 1

Hello @aik,

Thank you for taking time to post your question on Microsoft Q&A forum.

You can get exceptions from test in [TestCleanup], but for [TestInitialize] and some other attributes, this doesn’t work.

I would like to share a ticket with you => UnhandledExceptionEventHandler in MSTest doesn’t show the exception.

Extract some parts of the dialogues here:

MSTest framework, as most test framework, is catching "all" exceptions that occurs (on the same thread) during "test method" execution and consider test as failed. Because all the exceptions are caught, it’s expected that the AppDomain.UnhandledException doesn’t trigger as there is no uncaught exception. If the exception happens on a different thread then the UnhandledException will be triggered.

If the [TestMethod] fails you can check in [TestCleanup] and log it (and take a screenshot of the page, which is usually very helpful). However, if it fails in [TestInitialize] or [TestCleanup] you cannot check it and are forced to wrap the whole method in a try-catch to make sure everything went OK or take a screenshot otherwise.

I think you have some misconceptions about the unhanded handlers work. As we are directly catching the exception it would never bubble up in this path and this is the correct behavior.

Would it be feasible for MSTest to provide an UnhandledException event handler at the TestClass level?

Technically we could provide some handler (cannot be Unhandled because the exceptions are handled) but what would you do? What I mean is that eventing system is a trigger not awaited so by the time you act on it, it’s possible we have disposed the class, or run some other method that would change the state.

Now if you would like to easily inject some TestCleanup method behavior in all classes, this is something that would be different, would be part of the workflow (and awaited) giving you a change to act. And given some discussions we had would be indeed something valuable. Note that for the time being, if all your tests inherit from a base class with such TestCleanup method, it would be called always and would help you have this feature already.

Sincerely,

Tianyu

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