Technology Toolbox

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Jeremy Jameson - Founder and Principal



TDD in the Real World, Part 1

This post originally appeared on my MSDN blog:

Since I no longer work for Microsoft, I have copied it here in case that blog ever goes away.

Earlier today I presented a "Knowledge Transfer" session to a team of developers on my current project. If you've ever worked with consultants, you've probably experienced a "KT" session or something similar. In essence, it's just a meeting intended to cover one particular feature area of the solution and provide an opportunity for the "maintenance" team (i.e. people responsible for supporting and enhancing the solution going forward) to ask questions of the "development" team (i.e. the people who built the feature).

One of the topics I listed in the agenda for the KT session was around unit testing and Test Driven Development (TDD). This topic was of particular interest to the audience, which really wasn't surprising considering it was also a hot topic at a session I presented at Microsoft TechReady over a year ago.

I'll be the first to admit that I wasn't exactly an early adopter of TDD (at least not the principles we typically associate with TDD today). Sure, I've been creating unit tests for practically as long as I can remember writing code. Okay, not quite...but I can honestly remember creating XML input and output files that served effectively as unit tests over ten years ago while I was at Micromedex working with C++ and CORBA.

I started using NUnit years ago, but sometime around 2005 I switched over to the Visual Studio tools (for obvious reasons). I recall an internal training session presented by Martin Fowler in which he explained the concept of writing the test first, ensuring it fails, and then writing the code to make the test pass.

When I first started using NUnit, I kept thinking to myself: "This is great!...However, while it's really easy to do TDD when you are writing something simple like a Calculator service, it's often difficult to do it in the real world." Even after reading Extreme Programming Adventures in C# a few years ago -- which is a very good book, by the way -- I still find it difficult sometimes to use TDD when creating enterprise solutions with numerous external dependencies (backend databases, SharePoint, etc.).

It's been well over 5 years since I worked on a "pure" .NET solution; rather most of my time is spent working on solutions based on SharePoint, and much less frequently these days, BizTalk Server. I also get called in occasionally to do something spiffy with SQL Server and Analysis Services.

Sometimes I dream about how nice it would be to just build something with nothing more than what comes out-of-the-box with Visual Studio and the .NET Framework. Things like ASP.NET MVC just seem so developer-friendly. Of course, then I start thinking about all the really cool things you can do with SharePoint -- even if it does make life more, um, challenging in some regards.

The way I approach TDD is to do it where it makes sense, meaning that it adds more value over the long run than the effort you put into it. Many people might argue that TDD should be used all the time, but I doubt those people spend most of their time working on SharePoint solutions ;-)

Last year I watched a recorded webcast about doing TDD with SharePoint, which focused heavily on using Typemock to workaround the fact that the SharePoint API isn't TDD-friendly in the slightest. Note that I have essentially zero experience at present with any of the mocking frameworks out there. Sure, I've heard of Typemock, RhinoMock, and Moq -- and seen plenty of code samples demonstrating their use -- but there's just something about them that doesn't feel right to me.

While I certainly like the concept of creating true "unit tests" -- instead of "integration tests" -- and isolating external dependencies as much as possible, one thing kept nagging at me throughout the webcast until finally the presenter admitted it near the end of the session...

While the "unit tests" they created with TypeMock were all passing (i.e. green), when they subsequently ran the code within an actual SharePoint site, they found that the solution broke in several areas and they ended up writing a different set of "integration tests" to account for the different behavior. When I heard that part of the webcast, it only solidified my previous perception of mocking. Now, to be honest, I really don't know how much code churn was necessary after integrating with the live SharePoint site (the presenter didn't say).

Were they better off as a result of using TDD and Typemock? Probably.

Was the investment in mocking the SharePoint API worth it? I certainly hope so.

The reality is that sometimes mocking is definitely the way to go -- heck, maybe even most of the time (depending on the technology stack you are working with). Perhaps I'm overly biased by the fact that I, personally, find the code for unit tests that utilize one of the mock frameworks just so darn cryptic and difficult to read. I'm sure part of this is just that I really haven't sat down and devoted the necessary time to learn one of the frameworks. Of course, I also find LINQ and lamda expressions much harder to read than plain ol' C# code -- but perhaps that's just me ;-)'s getting late and this post isn't really going in the direction that I originally intended. What I really wanted to do was demonstrate a couple of real world examples of TDD that I've used, but I think I'll punt that until tomorrow morning.

I realize that this post might serve no other purpose than as "flame bait" for those of you out there that thrive on one of the mock frameworks that I mentioned above. Heck, if you are successfully using Typemock or some other mocking framework extensively with SharePoint -- and you're truly happy with the ROI (meaning you get decent code coverage and don't encounter lots of issues in your "green" code when you deploy it to a live SharePoint site) -- then I'd love to hear from you. As I've said before, feel free to "flame away" -- I can take it ;-)

Otherwise, stay tuned for part 2 of this post where I'll show you some of my "developer tests" (note that I often mix "unit tests" and "integration tests" in my ".DeveloperTests" projects, because in my mind, both of these types of tests add value, but sometimes one is more appropriate than the other).


  1. # re: TDD in the Real World, Part 1

    April 8, 2010 1:10 PM
    Frank de Groot

    I've done some projects that relied heavily on mock testing and found some major concerns:

    * Dependency Injection just to allow mock testing adds a lot of plumbing to your code.

    * You need to assume that the stuff you mock works the way you THINK it does. Especially with third party APIs that's a big assumption.

    * A mock test often repeats what the SUT does. Traditional unit tests (and integration tests) allow you to focus first on what goes in and should come out and then figure out how the heck to make that happen.

    * Refactoring often changes the interaction of a SUT so when refactoring you often need to change both the SUT and the tests. That way you can't now if you actually broke anything.

    * Some developers have a hard time understanding the idea of mock testing.

    So in practice I often got what you described: code still fails and looks cryptic.

  2. # re: TDD in the Real World, Part 1

    April 18, 2010 12:59 PM
    Thomas Eyde

    Ron Jeffries once said in a blog comment, I believe, that he prefers to write his unit tests using the real thing. I don't remember the reasons he gave, but I can imagine them and how they fit my own experience.

    My first, major mocking attempt was with Rhino mock and the Record-Replay syntax. I failed miserably: Not only did I forget to actually implement my mocked interfaces, no one but me understood what this was all about, so I had to maintain these tests even when someone else broke them.

    Needless to say, they went out one by one, because the investment was higher than the return.

    These days, I follow Ron Jeffries advice and add my mocks when it makes sense.

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