Introducing unit tests to a large evolving application


This session presents a case study of adding unit tests to a large existing .NET project. Learn from our experience what went well, what didn't go so well and what we did about it.


The application is more than 5 years old and has recently been converted from Visual Basic 6 to .NET 2005. It's a large application (estimated, not counted : 800 classes, 600.000 lines of code, 50 developers, 20 functional modules). The application is used by thousands of employees daily.

  • Is it possible to add unit tests to such an application?
  • How much effort does it take?
  • Is it worth all this effort?
  • How do you approach such an undertaking?
  • What should I do?
  • What should I not do?
This session presents the results of this ongoing project.

Benefits of participating

Learn from our experiences retrofitting unit tests to an existing large application. Some of the material is specific to the .NET environment, but most of it is applicable to any technology.

What will the organisers learn

Exchange ideas and tips with people who have experienced similar situations.

Session Outline

  • Introducing the application.
  • Introducing where we came from.
  • What convinced the team to do unittests ?
  • How was the team supported to write good unit tests ?
  • TestDriven or not TestDriven ?
  • Obstacles we encountered
  • Solutions we applied
  • What now ?