Testing Frameworks For Small Projects?

I know this question has been asked before, but none of the existing SO questions provide an adequate answer for my specific case.

I'm the lone developer working on a project mostly during free time. I'm approaching 100 classes so far, and I'm starting to realize that testing that many classes is becoming daunting. Especially as I go back and add in operator overloads for =, <>, CType, and Not; implement IComparable(Of T), IEquatable(Of T), IEqualityComparer(Of T); and overriding base methods like Equals and GetHashCode.

My current testing method has been to randomly scribble out some Debug.Print code for a specific class/method on a dummy form behind a single button, run the project, click the button, and make sure the Debug window has my expected value. But this is both tedious and starting to become a time waster.

What I know that I need to do is for each and every class, draft up a set of tests specific to that class to test its functionality. So I go and look at testing frameworks like NUnit, Gallio/MbUnit, etc. But I really don't see the value in them. It so far seems that I could just write a dedicated test class for each implemented class, wrapped in #If DEBUG/#End If blocks, and link those to a bunch of buttons on a large form to run my tests.

But that could take weeks at my current rate. So I ask SO for their opinion on how to approach something like this. Am I better off figuring out how to integrate one of these open source testing frameworks into my project? Or should I just write a bunch of testing classes and output their data somewhere?

I use VB Express 2010 and VS 2010, depending on which computer I'm on so I'll need to be able to do testing in both.