Getting Started with TDD?

Question

We are in the initial phase of trying to implement TDD. I demo'd the Visual Studio Team System code coverage / TDD tools and the team is excited at the possibilities. Currently we use Devpartner for code coverage, but we want to eliminate it because its expensive. We have very limited experience in TDD and want to make sure we don't go a wrong direction. Currently we are using SourceSafe for source control but will be migrating to Team System in about a year.

I can tell you our applications are very data centric. We have about 900 tables, 6000 stored procedures, and about 45GB of data. We have lots of calculations that are based upon userdata and different rates in the system. Also a lot of our code is based upon time (calculate interest to the current date). Some of these calculations are very complex and very intensive (only a few people know the details for some of them).

We want to implement TDD to solve QA issues. A lot of developers are forced to fix bugs in areas they are not familiar with and end up breaking something. There are also areas that developers are almost afraid to touch because the code is used by everything in the system. We want to mitigate this problem.

I'm afraid since our code is so data centric that implementing TDD might be a little bit more complex than most systems. I'm trying to come up with a gameplan that I can present to management but I want to hopefully not get caught up in some of the TDD beginner mistakes. Also if tools / facilities in Team System make TDD more complete then that would be nice but we don't want to wait for Team System to get started.

The first question we our asking is should we just start with the tools in visual studio? I have read post were people complain about the intrinsic tools in visual studio (need to create a separate project to create your test) but the one thing about the tools in visual studio is they are free and the integration is good. If we decide to go the other route in using something like XUnit, MBUnit, or NUnit then we are most likely going to have some maybe significant cost:

1) If we want IDE Integration (failed to mention most of our code is VB.Net)
---TestDriven.Net or Resharper or ?????

2) If we want code coverage
---NCover (Seems pretty pricey for its functionality)

Also I've seen some pretty cool functionality demoed in visual studio 2010. Like the ability to do input testing (data entered on a form) or the ability to record what the user has done and then feed that into your unit test to reproduce a problem.

Also, although I don't quite grasp the mocking object concept yet, I know a lot of people feel it's a must. The question is can all the mocking frameworks plug into visual studio's version of TDD (MSTEST)?

I have advised management that we should probably just add regression testing going forward (new development or found bugs) but not try to go through all our code and put in unit tests. It would be WAY too big of project.

Anyways, I would appreciate anyones help.

Answer 1

First thing to do is get this book:

Working Effectively with Legacy Code

For such a large project, read it and internalize it. TDD on a data driven application is hard enough. On a legacy one you need some serious planning and effort. Worth it in my view, but it is still a big curve.