Usually, when writing code, you adhere to some conventions on how your stuff should work. At least I hope you do – otherwise your code is probably a mess!

Sometimes, these conventions can be enforced by using some patterns to allow for compile-time checking – one example, that I can think of right now, is using the visitor pattern to implement multiple dispatch, which is explored a little bit in another post.

But what about conventions, that can only be checked at runtime? Well, how do we usually check stuff that can only be checked at runtime? – by writing tests, of course!

One project I am currently involved in, is written in ASP.NET MVC. All form posts are done using the automatic binding features of the framework, and I am following the convention that the names of my view models should end in “Form” – so as to enabling me to easily distinguish my form posting DTOs from my other view models. What is more natural, then, than performing the following test:

That is, I am running through all controller types, getting all actions, and checking the the parameter types are either in the array of accepted types (IsPrimitiveType) or a “true poco” (which in this application is a simple view model whose name ends with “Form” and comes from the right assembly).

This way, I will always know which types are used to deserialize forms. Great! But what about that pesky MissingMethodException whenever I forget to provide a public default contructor in my form models? Easy as cake! That part is checked by the following test:

These two tests combined, will assert that nothing will go wrong when submitting forms in my ASP.NET MVC project. That’s just nifty! And I really like the notion that I am helping future me.

Helping future me
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