George Mauer is on the Net

Re: What is Unit Testing?

In a post last month Zachariah Young posts that 

… unit tests … verify that the business logic is correct.  I believe that for it to be unit testing it has to use a testing framework like nunit or junit.

I say thar be dragons!  Tying your understanding of unit testing to a specific tool allows you to neatly sidestep thinking about whatThar be dragons  testing actually does.  Additionally, you deny credit to an excellent tool like NUnit by pigeonholing its purpose.

Consider for a minute what NUnit actually is.  Yes their own website claims that they are specifically a “unit testing framework for all” but what does it actually do?  In my opinion it is a framework for setting up an application’s state, executing code, and then asserting that the resulting state is as you expected. That’s pretty broad.  Way broader than the confines of mere unit testing.  

Take the excellent WatiN or (no longer maintained) NUnitASP tools.  Both can be run using NUnit but neither is used to build a true unit test.  WatiN for example remote controls your browser to investigate how your page will react to certain stiumuli.  What unit does WatiN test?  Your Page_Load method?  Your page renderer?  Whether the viewstate persists that you had entered some text halfway up the page before submitting and the text is not cleared when your page returns with a validation error?  The localhost routing mechanism on your PC?  Or does it test the integration of all of these?

I made the same exact mistake myself when I decided to ‘see what this TDD thing’ is all about last April.  I ultimately had to delete my entire testing project after I came to the realization that each test bit off far too large a chunk making it utterly impossible to maintain once true refactoring started.  I nearly cried that day.

But out of the ashes I was reborn with what I hope (but don’t really expect) to be the final zen-like understanding of this unit testing thing.  The first aha moment was when I finally caved in and decided to learn Rhino Mocks and my understanding sharpened when I caved again and looked into the new Rhino Mocks 3.5 AAA syntax.  Overall the lesson seems to be that I’m always wrong and I will eventually give in on everything and like it.  My girlfriend will be happy to hear that.

Let me tell you how I understand unit testing now.  Imagine a room.  You are standing on the outside and can comunicate with its ouccupants through a two way loudspeaker.  This room is your unit – if it helps you can imagine the room as painted black.  Now in testing you present your unit with a problem:

Given that you are on 735 Bourbon St New Orleans, Louisiana how far is it to my grandmother’s house?

I used to think that unit testing involved merely waiting for the answer:

Your grandmother’s house is 1345 miles away and you haven’t visited in months you shmuck.

Now I realize its more about everything else that is said.  “Where does your grandmother live?” and “Can you be so kind as to  slip an atlas under the door?” should definitely be questions that you hear over that loudspeaker.  If you’ve separated your resposibilities properly the unit will also require a calculator that given two points on a map can tell you the distance (the specific calculator implementation should depend on whether you intend to fly or use the highway system).  The unit might even request that you hang a EnRouteToGrandmas = true sign on the door.  

The point is that you’re not so concerned with the final answer as much as you are with the unit asking the right questions.  Afterall, without that information know that it could not possibly be doing what you mean for it to do!

And so I define unit testing as

Verifying that given an input, a piece of code makes all the external requests that you would expect where the unit is small enough that the number of these can be enumerated with ease.

Note that this definition does not necessitate automated testing and this is something that I again think is basically correct.  After all, a framework should not do anything that you cannot do for yourself.

The beautiful part is if you’re limiting the amount of requests that you’re going to expect – let’s say no more than four – single responsibility emerges almost all on its own.  After all, how much can a piece of code do if its not communicating with the external world?

So there you go, thats my understanding of unit testing.  I look forward to being proven wrong in the future and having to refactor everything all over again.  But until that time,  Zachariah, you’ve been blogo-served!

Disclaimer:  I do not know Zachariah personally but he seems like a smart guy that is highly involved in the ALT.Net community.  I do not purport to be more knowledgeable than him in programming issues, I just disagree with him on this one point.

kick it on


January 15, 2009 Posted by | ALT.Net, Programming | , , | Leave a comment

Let’s try to start this nice and simple

So since I registered this blog name I have proven empirically that I am incapable of actually writing to it so I figure I’ll start simple – with a list.  And – because this is what i’ve been reading and thinking of a lot lately – its going to be programming related.  Weeee.   So here we go.

Technologies that I HAVE to learn:

  • NHibernate – The list, podcasts, and .NET blogs have been a buzz about this for so long that its barely even mentioned anymore, but yes, through argument and experience I’ve been convinced, dynamically generated SQL is the way to go.  Time to get a crackin’.
  • MbUnit – Apparently that’s what a lot of the pros use and I want to  be a pro right?  Well, I’ve got the basic [TestFixture] – [Test] – [RowTest] stuff down but guys like Phil Haack have to love it for more than just a few neat features and a nice GUI right?  How about reading the documentation?  Also, what the fuck is Gallilo and how come I can’t get it to run?
  • StructureMap or Castle Project – Inversion of Control / Dependency injection frameworks.  This is what you use if you want an extensible application.  And I do.
  • F# – A couple months ago, I realized that I kinda like programming in Javascript. Apparently, I’m not the only person that thinks so.. I guess it was because I was finally starting to get an understanding of what this functional programming thing is all about. And now that that I know, I like it!
  • And in a similar vein – JQuery. – Yeah, I’ve gotten some practice with this amazing toolbox in working with my personal site and The Roots Of Music and I think there’s something there. I want more, a lot more.
  • Git or Mercurial – Distributed Version Control Systems.  These seem to be the new thing in version control, no pressing need to switch from SVN, but I should start getting familiar with them.  It seems like for the time being, Mercurial is the shiznit.  Not sure if any of them have nice TortoiseSVN-style support though.
  • TypeMock – Commercial mocking software.  Type mocking is really just something that I need to learn about as I’ve run into the limits of non-mocking unit tests already.  I’ve heard this product is good in a few places and they have a good learning section the web-site as well as a free download version.  Could be worth trying it out.  As an alternative, we’ve also got Rhino Mocks which is free.

May 3, 2008 Posted by | Music, Programming | , , , | Leave a comment