Tag Archives: Code Cast

Legacy Coderetreat: Episode 9 – Extract Pure Functions – Code Cast

Extract Pure Functions – 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.

In the first episode we wrote some characterization tests with the purpose to create a basic safety net. Now we continue to refactor the code, starting from there. We already have some tests running and we want to have methods that do only one thing; we want to apply the Single Responsibility Principle. A really good tool that can help is using pure functions. We extract functions, make them static and then make sure the function does not have any side effects. These functions help me clean the code and help me start structurig the code according to clear responsibilities. At a later time we will extract all these functions that have similar responsibilities to a new class.

Read here more about this concept in my blog post.

 

Legacy Coderetreat: Episode 8 – Use Mocking Framework – Code Cast

Use Mocking Framework – 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.

In this code cast you can see how to start using mocking framework on an existing code base. Once we have an interface, we can start using the mocking framework to test external dependencies.

After extracting new and clear methods from the messy code and after extracting classes, we now have a code base with clearer dependencies. However, once we understood how to do dependency inversion, testing the core system becomes a bit more difficult. We need to write tests to show how the core system collaborates with the dependencies we inverted. For testing collaboration with inverted dependencies we use mocking framework.

Read here more about this concept in my blog post.

 

Legacy Coderetreat: Episode 7 – Extract and Override – Code Cast

Extract and Override – 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.

Extract and Override is a very useful technique to break static dependencies. Whenever we cannot write tests for a piece of code, it is often because we have static dependencies. In the code cast below you can see how to use extract and override having a random number generator very tightly coupled. Because of that, we cannot have the same output for some clear steps. The solution found in this video is to extract the random to a new method and then override the random generator, just for tests. In this way we have predictability for tests.

Read here more about this concept in my blog post.

 

Legacy Coderetreat: Episode 6 – Dependency Inversion – Code Cast

Dependency Inversion – 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.

During this code cast you will see how to use the concept of Dependency Inversion on a legacy code base. Dependency Inversion is one way of transforming a tightly coupled system into a system that has a core and many small external dependencies. These external dependencies can be called also plugins. Read more about this concept in my previous blog post.

 

Acknowledgements

Many thanks to Thomas Sundberg for proofreading this post.

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: 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: Episode 2 – Golden Master Code Cast

Golden Master – 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 where I start generating system test with the Golden Master technique. Please read more details about this technique in the Part 3 – Golden Master blog post. Have fun!

 

 

 

Legacy Coderetreat: Episode 1 – From Nothing to System Tests Code Cast

From Nothing to System Tests – 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 where I start covering with tests a simple code base. Please read the explanation of this technique in the Part 2 – From Nothing to System Tests blog post. Have fun!