Tag Archives: Existing

Legacy Coderetreat: Part 16 – Refactor Conditionals by Decomposing Conditional

Refactor conditionals by Decompose Conditional

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.

IF-THEN-ELSE-END_flowchart

Purpose

We often see code with conditionals that are hard to understand. The purpose of this technique is to make the code look readable by extracting a function with the condition. It will be easier to test the code if the condition is extracted and injected as a dependency.

This technique is useful when having good variable names is not enough to explain the condition. We can have some of the following reasons for wanting to extract a function with the condition:

  • The condition is duplicated in several parts of the class
  • The condition is duplicated along different classes
  • Test the condition in isolation, because of its complex nature
  • Test the code without understanding how the conditions work (inject conditions as stubs)

 

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Legacy Coderetreat: Part 15 – Refactor Conditionals by Explaining Variable

Refactor conditionals: Explain Variable

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. Refactor Conditionals - Explain Variable

Purpose

When you try to read a code base that has many conditionals, often the problem is that the condition itself is very hard to understand. This technique improves the conditionals by making them clear and very easy to read. Read More →

Legacy Coderetreat: Episode 13 – Document Possible Bugs with Tests – Codecast

Document Possible Bugs with Tests – Codecast

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 codecast in Java.

In the previous episodes we reach the moment when we extracted one simple class. We used the The Rule of Three and pure functions. This newly extracted class is covered with characterization tests. Then we wrote some unit tests in the following episode. But some of the behavious seemed strange, and we thought they might be bugs.

Because we are never sure when working on existing code if some behavior is a bug or a feature, we want to document all the suspicious cases. In order to do that, I am presenting three methods: use an annotation, prefix the test, use a different class.

Bug or feature? Check out the codecast to see all of them in action.

Read here more about this concept in my blog post.

When we document defects with tests it is a good idea to group all the tests documenting possible bugs one after the other. The discussions with the business persons are easier and you do not need to search the next test again and again.

Always discuss with business persons before changing the code. Often one might think they understand what the code does, but the situation if often very different in practice. Think to verify every detail with business analysts before changing the existing code.

Legacy Coderetreat: Episode 12 – Unit Testing on Legacy Code – Codecast

Unit Testing on Legacy Code – Codecast

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.

Codecast

This is a codecast in Java.

In the previous episodes we reach the moment when we extracted one simple class. We used the The Rule of Three and pure functions. This newly extracted class is covered with characterization tests. But that is not enough, we want to continue adding other types of tests to understand the system better.

This is why during this episode you will see how to add unit tests to code extracted from a legacy code class. These tests have a small granularity level than the characterization tests we already have. This is the moment to dive more into details.

See this video to understand how you can document the current state of the system, by unit testing on legacy code.

Read here more about this concept in my blog post.

We started with a class having non-public methods. The purpose of this session was to start covering the class with tests. In this moment we have short and clear unit tests, written in isolation of any slow dependencies. These tests are fast and we need to run then any time we will change the production code, to make sure we do not introduce defects.

In the same way as shown in the last blog posts, we can extract pure functions, extract classes and then cover these classes with unit tests.

Legacy Coderetreat: Episode 11 – Extract Class – Codecast

Extract Class – Codecast

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 previous episodes we restructured some parts of the code base. We also extracted pure functions and applied The Rule of Three when restructuring the code.

Because we have extracted some pure functions, now we need to think if those pure functions belong to new classes. So we structure the functions in a way that they belong together from the point of view of their responsibilities. After structuring the functions we extract the class.

Learn from this video how to extract a class in legacy code in such a way that you do not introduce side-effects to the existing behaviour.

Read here more about this concept in my blog 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

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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

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Legacy Coderetreat: Part 8 – Extract and Override

Extract and Override

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

Almost always when needing to test existing code we bump against dependencies that make the system untestable. This technique is useful to extract the static dependencies. After that we can use dependency inversion in order to be able to really test the systems.

With this technique we can transform untestable systems into testable systems, step by step. The steps are small because we want to enable safety while changing the code.

Extract and Override

Extract and Override

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