Tuesday, September 06, 2011

Guided By Tests

Last week I started a TDD experiment at work. I gathered some interest from management and then sought out participants with a very simple concept: build an application in 5 days, over lunch hour, using nothing but unit tests to drive development.

My next few posts will be part of a series that shares the details of that experiment.


Over the years, I've had many conversations with colleagues about TDD. One of the most common comments made is that they don't know what to test or where to start. Another common theme is the desire to get into a project at the very beginning where all the project members have bought into the concept. I've always found this comment to be strange. It's a great comment and it makes perfect sense but -- why the beginning? Why not the middle or end of the project after the tests are put into place? I sense they're expressing two things. First they're expressing the obvious, that life for the development team would be much different if they had tests from the beginning. And secondly, they're interested in understanding how the team managed to establish and sustain the process.

The goal of my experiment would show how to start a project with TDD and to walk through the process of deconstructing requirements into testable components. The process would use tests as the delivery mechanism but would also showcase how to design software for testability using separation of concerns and SOLID OO design principles. Requirements and documentation would be deliberately vague, and the application would need to showcase common real world problems. The tricky part would be finding an application to build.

Fortunately, I was recently inspired by a post by Sacha Barber that provides a great example of how to use the open source graphing framework Graph# to build a graph application in WPF. I immediately saw how I could use this. My current project uses NDepend for static analysis and as part of the build process it produces an image of our dependency graph. With over 80 nodes and illegible text, the static image is mostly useless. However, the build process spits out the details for the graph as an XML file. With some simple xml parsing, I could use Sacha's example to build my own graph.

So rather than spending my weekend working on this application, why not turn this into a teaching exercise? (Ironically, I'm spending my weekends blogging about it)

Follow up posts:

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