[.Net] Is it possible to change the way unit tests are invoked?

Question

My guess is that the current semantics of unit testing involve actually calling the method, i.e., if I have a method MyTest() then that's what gets called. My question is this: is it possible to somehow change the pipeline of the way tests are executed (preferably without recompiling the test runner) so that, say, instead of calling the method directly it's called via a wrapper I provide (i.e., MyWrapper(MyTest))?

Thanks.

Answer 1

It depends on how the unit testing framework provides interception and extensibility capabilities.

Most frameworks (MSTest, NUnit etc.) allow you to define Setup and Teardown methods that are guaranteed to run before and after the test.

xUnit.NET has more advanced extensibility mechanisms where you can define custom attributes you can use to decorate your test methods to change the way they are invoked. As an example, there's a TheoryAttribute that allows you to define Parameterized Tests.

I don't know MBUnit, so I can't say whether it supports these scenarios or not.

Answer 2

If you use MbUnit then there's lot of stuff you can customize by defining custom attributes.

The easiest way to do this is to create a subclass of TestDecoratorAttribute and override the SetUp, TearDown or Execute methods to wrap them with additional logic of your choice.

However if you need finer control, you can instead create a subclass of TestDecoratorPatternAttribute and override the DecorateTest method with logic to add additional test actions or test instance actions.

For example, the MbUnit [Repeat] attribute works by wrapping the test's body run action (which runs all phases of the test) with a loop and some additional bookkeeping to run the test repeatedly.

Here's the code for RepeatAttribute: http://code.google.com/p/mb-unit/source/browse/trunk/v3/src/MbUnit/MbUnit/Framework/RepeatAttribute.cs