Tag Archives: Existing Code

Talk: Agile Lean Europe 2014 – Legacy Code is Fear

Legacy code is fear because we fear the unknown. Learn what you need to learn in order to be less scared about legacy code during this talk.

You are a programmer. Someone from the company comes with an idea to add a feature and they are sure this new feature is very easy to add. And it should be. But the code is old. The code is a mess. Nobody in the firm knows any more that part of the system. You need to change that ugly piece of code. You are afraid that you might introduce defects. Legacy code is fear.

 

Here are the slides for the talk Legacy Code is Fear:

Legacy Coderetreat: Episode 5 – Basic Rules of Refactoring – Code Cast

Basic Rules of Refactoring – code cast

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

Code Cast

This is a code cast in Java.

We start by checking what can be extracted to another method. The Basic Rules of Refactoring describes the detailed steps I use.

To ensure that we have a safety net, let us start with covering the code with some system tests and then write tests on the newly created method. These are also characterization tests, but they are often simpler than the system tests we wrote before. When the new method have been covered by tests, call it from the initial place where the code was copied from. Run all the system tests. At the end do some manual testing to see that everything works fine.

This technique is very useful to have small and safe steps while refactoring. Remember to never cut and paste. Always duplicate the implementation, cover it with tests and then reroute the call to the new code.

 

 

Acknowledgements

Many thanks to Thomas Sundberg for proofreading this post.

Legacy Coderetreat: Episode 4 – Add Feature on Legacy Code – Code Cast

Add feature on legacy code – code cast

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

Code Cast

This is a code cast in Java. We have a new feature request and we need to add it to a legacy code base.

We start by understanding what we need to change. After that we run the existing system tests, that we wrote during the session From Nothing to System Tests. We use a test coverage tool to understand how much of the code is covered with tests. After this step we start writing new system tests until all the code
that will be changed is covered by tests.

When all of the system is covered with tests, we refactor the code to make room for a new feature. We extract a method, then a class and then an interface. The interface is implemented in a new way so that we add the new functionality. Adding the new functionality is done with tests written up-front.

At the end we write one system test to verify that the whole system can work well with the new feature. This is a kind of partial acceptance test that helps us understand if all the system works well together. And of course, manual testing and refactoring is essential before we can say we are done.

See more about the technique in the blog post Add Features on Legacy Code.

 

 

Acknowledgements

Many thanks to Thomas Sundberg for proofreading this post.

Legacy Coderetreat: Part 12 – Extract class

Extract Class

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

Purpose

When working with existing code we need to look at the responsibilities of existing classes. If one class is too big, we need to extract new classes from that initial class. A class too big means that it’s not respecting the Single Responsibility Principle.

Extract Class

Extract Class

Read More →

Legacy Coderetreat: Part 10 – Extract pure functions

Extract Pure Functions

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

Purpose

We have some class that is very big. We want to divide the existing code into more methods and classes so that we have in the end some code that is easier to understand. If the methods are small, they are easy to change. In the same time the code would respect the Single Responsibility Principle. We optimize our software for changeability. In the following we will see how we can extract pure functions to achieve that.

Pure functions

Pure functions

Read More →

Legacy Coderetreat: Episode 3 – Fix bugs on Legacy Code – Code Cast

Fix bugs on legacy code – code cast

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

Code Cast

This is a code cast in Java. I have a bug report and I need to fix bugs on legacy code. I start by writing characterization test on the system level and then I dive into the code with writing a unit test. See more about the technique in the blog post Fix a Bug on Legacy Code.

 

Legacy Coderetreat: Part 1 – Introduction

Legacy Coderetreat

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.

A bit of history

On 26 November 2011 I had the honour of being an attendee at the second ever Legacy Coderetreat, which was supposed to be the first one in the world. But my friend Johan Martinsson from Grenoble beat Erik and me to it. Anyway I was part of the second ever Legacy Coderetreat in the world, facilitated by JB Rainsberger. JB had come with this concept of using the Coderetreat format, but for legacy code.

At the beginning of the day he presented us the problem, like in any other coderetreat. The problem was an ugly trivia game and you can find the sources here. At that time the code base was translated, from Java, only in a couple of other languages. Now you can find almost any language you want, thanks to the worldwide community of passionate developers who translated the code base.

JB facilitated the event like you could find in here, with a lot of details. But in short we would start with a free session, then follow with Golden Masters, continue with Subclass to Test, Replace Inheritance with Delegation and then Pure Functions. After each iteration we deleted the code like in any other coderetreat and swapped the pairs.

I liked a lot the fact that JB started this idea, because I am a big lover of working with legacy code. And this Legacy Coderetreat is such a good way to practice. But I had some other ideas on how to make it different.

legacy-coderetreat

Legacy Coderetreat

Read More →