Add an attribute to the Assert class

- [Voiceover] I'll review the code that's…in my TestRunner project in this MainWindow.xaml.cs file.…In the Button Click handler I'm instantiating…an instance of my test class,…and then I'm calling each of the test methods…that are inside that class.…This works for simple projects,…but it's simply not gonna scale…when I start adding multiple unit tests.…Here's what I mean:…I have this Brokerage library,…and I have this Commission Calculator class,…and I've decided I need to write…some unit tests for that too,…so I go to my Testing library,…I'd add another testing class,…and then I'd add several testing methods.…

For this example, let's say we've added 18 test methods.…Then I'd have to go back to my Button Click handler…and instantiate my new test class,…and then have a line of code inside this click handler…for each of the methods I need to invoke.…That's simply not gonna scale if I have hundreds…or thousands of unit tests.…What I need to do is find a way in .net to tell…the TestRunner which methods inside the testing library…