Many people ask, “How do I find time to refactor?” I think the question itself betrays a misunderstanding of refactoring. The solution, therefore, does not lie in finding ways to convince a product manager to schedule “refactor time” but in changing our way of thinking. Let me tell you when I refactor.
Some people think that programming is about making the code work. And at a basic level, it is. But programming is about so much more.
Programming is about managing an ever-changing code base. It is about satisfying concrete requirements today while being able to accept new requirements tomorrow. It is about being able to clearly communicate your intent across space and time to other developers who will read, modify, and extend your code. For that reason, programming is not about just writing code that works. It is about writing code that is easy to read, easy to reason about, and easy to modify.
Redefining being “done”
Getting the code to work is required but not sufficient. In test-driven development, we have the red-green-refactor cycle. Getting the code to work means going through red and green — getting the tests to pass. But refactoring is about that last step — about making sure the code we just introduced is clear and maintainable.
This is where the change in mindset comes in. As developers, we should think of our work as being “done” not just when the code works but when the code works and it is clear and maintainable.
That is why refactoring should happen all the time. There is no need to introduce a “refactor time” in the schedule. It is baked into the very definition of doing work.
Clarifying what refactoring is
Now, some might be hesitant to refactor all the time because they think it means making large breaking changes. But that’s not what refactoring is. At its core, refactoring is about changing the structure of code without changing its observable behavior. Take a look at the definition of refactoring from the Refactoring book:
Refactoring (noun): a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior.
So while we work, we should constantly try to improve the code without changing the behavior so that the code is easier to understand or cheaper to modify.
When to refactor
You don’t decide to refactor, you refactor because you want to do something else, and refactoring helps you do that other thing.
– Martin Fowler in Refactoring: Improving the Design of Existing Code
In practice, there are usually three instances when I refactor: as the last step of red-green-refactor, when trying to modify code that is difficult to understand, and when an existing design doesn’t work.
1. The last step in red-green-refactor
The first instance is when I’m test-driving a feature. As mentioned before, the red-green-refactor cycle has refactoring built in. So when I get the tests to pass, I take a few minutes to clean up any code I have introduced: use better names, extract private methods, extract classes, etc.
2. Code that is difficult to understand
When I am trying to add a feature or fix a bug, but I have to modify an existing piece of code that is difficult to understand, I refactor it (once I understand what it is doing). That way, I make sure I am introducing the correct change into the code base, and others in the future (myself included) will more easily understand it. We pay the tax of difficult-to-read code once, not every time someone has to read that code.
3. Existing design doesn’t work
Finally, I refactor when I’m trying to introduce something new, but it does not quite fit the existing design. I first refactor the design so that what I am trying to introduce is easy to add. This is what Martin Fowler calls Preparatory Refactoring. In the Refactoring book, he says:
When you find you have to add a feature to a program, and the program’s code is not structured in a convenient way to add the feature, first refactor the program to make it easy to add the feature, then add the feature.
Or as it is commonly said, “Make the change easy, then make the easy change”.
If you’re interested in practicing refactoring on a complicated piece of code, I recommend trying out the Gilded Rose Kata. It’s a very fun and illuminating exercise.
And if I communicate nothing else, I highly recommend reading the Refactoring book. It’s full of great information on how, when, and why to do refactoring.