About   Slides   Home  

Managed Chaos
Naresh Jain's Random Thoughts on Software Development and Adventure Sports
RSS Feed
Recent Thoughts
Recent Comments

Refactoring Legacy Projects: Scaffolding Technique

If you’ve inherited a Legacy Project (project without any tests) and say you want to enhance an existing feature, where do you start?

In such situations, I find myself building some form of workflow tests (scaffolding). I start off using a record and play back testing tool to record couple of scenarios for the feature, I want to enhance. Most often, I would take the recorded tests and covert them into a re-entrant, independent scripts. So that I can execute them over and over again, without needing manual intervention. Basically this would mean, automating the set up and tear down of the application’s external dependencies like data-stores, email servers, etc correctly. This should not take more than a couple of hours to configure.

This helps me build the initially safety net to start off. This also gives me a decent understanding of how the feature works. Now I can go inside the code, change something really small and see what impact it has on my tests. Some times I tweak my test to see what impact it has on the feature. Basically I’m using this test as a probe to gain deeper understanding of the feature’s functionality.

Doing this give me some confidence to jump in and start refactoring the code, so that I can create an inflection point, break dependencies and start writing unit tests around the core of my feature. In couple of hours, I should be able to build a solid safety net, around my feature using unit tests and/or business logic acceptance tests.

At this point, I almost always, go and delete the initial workflow test that I had built. This is the reason, I call this approach as the scaffolding technique.

  • Build some initial workflow tests to help you get in there,
  • Make the necessary code/config changes to write direct tests
  • Gradually build a solid safety net around the feature
  • The scaffolding (initial workflow tests) did its job, now its time to throw them away
I demonstrate this technique when we do the Refactoring Fest. We take VQWiki (an open source Java wiki, with Zero tests) and build our scaffolding using Selenium.

    Licensed under
Creative Commons License