Developers know that a software system will become more complex and more highly coupled over time as additional changes are made. Often this calls for refactoring or reengineering the code to make it more maintainable. Reengineering will allow you to incorporate what has been learned about how the code should have been designed. This is the kind of learning that was the original basis for the term “technical debt.”
So how should we go about reengineering code that remains vital and useful? In real life we keep applying metaphorical Band-Aids as we make changes and incorporate new technologies. This leads to design erosion. Many progressive managers now understand the debilitating nature of this erosion and how it affects quality and productivity.
Even if we agree that reengineering is called for, how can we plan for it? Here are four key steps to take if you have decided to reengineer your software.
1. Understand the current structure of the code. Always resist the temptation to reengineer without a clear understanding of what you have. Understand and identify the critical components and what their dependencies are. For example, if you are Java or a .NET programmer, understand the various JAR files or assemblies and how they are related to each other. For C/C++, understand the executables and libraries, as well as the code structure used to generate them. Now ask yourself: Are these the right components in my desired architecture? Sometimes you have only one component. If that is the case, ask yourself if you need to split up the component into smaller components.
2. Examine the internals of the components, particularly the larger ones and the more important ones. Look at the dependencies of the classes or files that constitute the component. Is there excessive coupling? Does this coupling make the code harder to maintain? As a team, decide what your desired architecture is. Consult senior developers. Ask the team members with different areas of expertise to validate your ideas. The testing team can be particularly helpful. A good architecture will make a huge difference in how easy and effective it is to test. You should be able to take the existing classes or files and build new components. Try various what-if architectures to arrive at the desired architecture for your existing code.
3. With the desired architecture in hand, you should now know what changes are needed and what the unwanted dependencies are. Prioritize the dependencies to fix based on your requirements. If you have areas of code that change frequently, you should think about componentizing them. Always take into account your current requirements. While reengineering has its own benefits, it is unlikely that you will stop making other improvements during this time. Any reengineering effort is likely to be in conjunction with other improvements. A good reengineering tool will allow you to perform reengineering work in conjunction with making continued enhancements to the product. Another benefit of this approach is that it will build management support for the reengineering effort.
4. The last step is to make sure you communicate the reengineering plan to the entire team. With a prioritized scheme, make reengineering a part of continuous integration. You can create rules that prevent things from getting worse by continuously examining the changes against the desired architecture. Reengineering stories should be part of agile planning just like any other stories. Not only can you do reengineering, you can make it part of your normal development. The best reengineering exercises often minimize disruption and still allow you to migrate to a new architecture.