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Have you ever looked at your code and asked yourself, "Who wrote this mess??" And suddenly you realized it is none other than you. I’ve faced this situation a lot—your own code seems like a mess if you review it after 2 or 3 months. Do you know the reason why? Yes, it’s because there is no refactoring in the code

In this blog, we’ll explore what code refactoring is, why it’s important, and walk through a few examples. Clean APIs often play a crucial role in effective code refactoring—we’ll also look at an example of that in the examples section.

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What is Code Refactoring?

Refactoring means restructuring your existing code without changing what it actually does. Basically, you’re making it cleaner, more readable, and easier to maintain.

Let me give you a simple example: code refactoring is like cleaning your room. Instead of just buying new furniture, you’re organizing what you already have so it’s easier to find things—and it also looks good. We can apply the same principles to code. We’re not going to add new features; instead, we are going to make our code clean, more readable, and easier to maintain.

Code Refactoring process

Examples of code refactoring are:

Removing dead code
Standardizing code formatting
Changing a local variable name to make the code less confusing
Renaming poorly named variables to make them more descriptive
Breaking up long lines of code that perform multiple functions to make the code easier to maintain

What is the Purpose of Code Refactoring?

Let me give you an example of the purpose of code refactoring. Let’s say you are working on a company project. In that scenario, you are not the only person working on the project there are many people involved, right?

In that case, if your code is not clean or understandable, it will be so difficult for others to review it. So, it’s not just for your personal projects you have to do it wherever you are writing code.

The best code, according to me, is when someone reviews your code and it clearly says what a particular part of the code is doing. For that, you need to refactor your code so that it will be understandable by anyone who reviews it.

When Should You Refactor Code?

We need to understand when code should be refactored. Here are some signs it’s time to refactor:

Your code works, but it’s hard to understand
You’re copying and pasting similar logic multiple times
It’s hard to add a new feature without breaking something
Tests are failing after small changes
Code reviews take too long because the code is unclear

You don’t have to wait for a big project rewrite. Refactor as you go. A small 10-minute cleanup during a bug fix or feature update can save you hours later.

When You Don’t Need Refactoring

We also need to know in what scenarios refactoring is not necessary:

If you can’t not do regression testing in a comprehensive manner post re-factoring
Another reason to not refactor is when you aren’t approaching the existing code base with proper humility and respect.

But in most scenarios, we need refactoring. If you can argue "my code base is not changing," then why do I need refactoring? It works now for today, but eventually it fails tomorrow. So don’t feel hesitant to do refactoring.

Techniques to Perform Code Refactoring

We have understood some basics of code refactoring. Now we can look at some of the techniques to perform code refactoring.

1. Extract Method (Breaking Down Large Functions)

Problem: A function is too long and does multiple things.
Solution: Split it into smaller, reusable functions.

python
def process_order(order):
    # Validate order
    if not order.items:
        raise ValueError("Order is empty")
    if order.total <= 0:
        raise ValueError("Invalid total")

    # Apply discount
    if order.customer.is_premium:
        order.total *= 0.9  # 10% discount

    # Save to database
    db.save(order)
    return order

After Refactoring (Extracted Methods)

python
def validate_order(order):
    if not order.items:
        raise ValueError("Order is empty")
    if order.total <= 0:
        raise ValueError("Invalid total")

def apply_discount(order):
    if order.customer.is_premium:
        order.total *= 0.9  # 10% discount

def process_order(order):
    validate_order(order)
    apply_discount(order)
    db.save(order)
    return order

2. Rename Variables & Functions (Clarity Over Cleverness)

Problem: Unclear names make code hard to understand.
Solution: Use meaningful names that reveal intent.

Example: Before Refactoring

python
function calc(a, b) {
    return a * b * 0.1;
}

After Refactoring (Better Naming)

python
function calculateTax(price, taxRate) {
    return price * taxRate;
}

3. Replace Magic Numbers with Constants

Problem: Hard-coded numbers make code confusing.
Solution: Use named constants instead.

Example: Before Refactoring

python
if (status == 2) {
    shipOrder();
}

After Refactoring (Using Constants)

python
final int ORDER_SHIPPED = 2;

if (status == ORDER_SHIPPED) {
    shipOrder();
}

4. Simplify Conditionals (Avoid Nested Hell)

Problem: Deeply nested if-else blocks are hard to read.
Solution: Use guard clauses or early returns.

Example: Before Refactoring

python
def login(user):
    if user is not None:
        if user.is_active:
            if user.has_valid_password:
                return "Login successful"
            else:
                return "Invalid password"
        else:
            return "Account inactive"
    else:
        return "User not found"

After Refactoring (Guard Clauses)

python
def login(user):
    if user is None:
        return "User not found"
    if not user.is_active:
        return "Account inactive"
    if not user.has_valid_password:
        return "Invalid password"
    return "Login successful"

5. Replace Temp with Query (Avoid Redundant Calculations)

Problem: Repeated calculations in a function.
Solution: Extract them into a separate method.

Example: Before Refactoring

python
def calculate_total(cart):
    subtotal = sum(item.price * item.quantity for item in cart.items)
    tax = subtotal * 0.08
    discount = subtotal * 0.1 if cart.has_coupon else 0
    return subtotal + tax - discount

After Refactoring (Extracted Calculations)

python
def calculate_subtotal(cart):
    return sum(item.price * item.quantity for item in cart.items)

def calculate_tax(subtotal):
    return subtotal * 0.08

def calculate_discount(subtotal, has_coupon):
    return subtotal * 0.1 if has_coupon else 0

def calculate_total(cart):
    subtotal = calculate_subtotal(cart)
    tax = calculate_tax(subtotal)
    discount = calculate_discount(subtotal, cart.has_coupon)
    return subtotal + tax - discount

Example of Clean API

Before refactoring:
```
python
func ProcessData(data []byte, userID string, config map[string]string, retry int) ([]byte, error)
```
It does multiple things: fetches user, parses config, retries processing… it’s hard to test, maintain, or change.

After refactoring:

python
type Processor interface {
    Process(input []byte) ([]byte, error)
}

You don’t need to apply all techniques at once. Start small. Every bit of cleanup improves your codebase! The above examples are just to show you how it works—there are many other refactoring techniques out there, too. Try it, and you’ll start noticing changes in your codebase. The examples I shared are intentionally simple.

Have you gotten bored of reading about code refactoring? I hope you are a little bored. Let’s look at something different! We’ve been talking about code refactoring, writing clean code… and let’s be honest, these things take time, right? Instead of building and shipping features, we’re often busy maintaining clean code. Let’s see how AI gives us confidence to do code refactoring.

How to use AI to do Code Refactoring

We heard about vibe coding, right? We can also try vibe coding using AI, but I didn’t experiment yet. Now, what are we waiting for? Let’s try code refactoring with GitHub Copilot!

Github copilot chat

You can also see the key improvements

Github copilot improvements

How to Use AI for Code Refactoring

I hope everybody tried GitHub Copilot – but also try it for other use cases too!

How to Do Code Refactoring with OpenAI Codex:

OpenAI recently released the Codex CLI – an open-source, lightweight coding agent that runs in your terminal.

Install it using npm:

javascript
npm install -g @openai/codex

If you don’t have an OpenAI key, don’t worry – you can try it with other model providers. I tried with Groq, I created my free key.

In the output, you can see I’m doing both vibe coding and refactoring just in the terminal!

Codex cli

Codex output

I just tried Copilot and Codex – you can try Cursor or any AI tool to refactor your code!

Worried About Testing After Code Refactoring?

We’ve seen how tools like Copilot and Codex help refactor our code but how can we use AI to write tests?

While Copilot can write tests, it’s a general-purpose model trained to handle a wide range of coding tasks. But what if there were a platform designed specifically for testing a vertical AI platform built just for that?

Sounds interesting, right?

That platform is none other than Keploy. You can use Keploy to automatically generate unit tests and API tests. Think of it as a no-code AI platform for testing — making test generation smarter, faster, and easier.

New AI Unit Testing Agents in the town

Unit testing agent

Keploy has recently released a Unit Testing Agent that generates stable, useful unit tests directly in your GitHub PRs, covering exactly what matters. How cool is this? Testing directly in PRs – so developers won’t need to write test cases for their new features. Keploy writes them for you! No noisy stuff – just clean, focused tests targeting the code changes. You can also try this Unit Testing Agent in your VSCode

Keploy Unit testing agent

VSCode Extension: https://marketplace.visualstudio.com/items?itemName=Keploy.keployio

PR Agent: https://github.com/marketplace/keploy

New AI API Testing Agent in the Town

Instead of writing test cases to test your APIs, what if you provide your schema, API endpoints, and curl commands to an agent, and it generates the test suite and gives you the test reports? Sounds interesting or confusing? Yes, it is possible! Keploy API Testing Agent will do all this without you touching any code.

To try an AI API testing agent: https://app.keploy.io/

Let me come back to the blog again.

What are the Benefits of Code Refactoring?

I think we don’t need to go deep into this section because we already saw the benefits of code refactoring in the previous sections. But here’s just a quick glance:

Benefits of Code Refactoring

What are the Challenges of Code Refactoring?

We saw the benefits of code refactoring, and now let’s look at the challenges—like why people are afraid of refactoring:

Fear of breaking working code if there are no tests
Time-consuming, especially in large codebases
Your boss may not see immediate value, as it’s not a new feature
It requires a deep understanding of the code
Lack of automated tests makes it risky to refactor

Best Practices for Code Refactoring

Analyze the code – Understand what the code is doing before making changes.
Refactor as a team – It’s not a one-man show; everyone should be on the same page.
Test at every stage – Always test after each change to make sure nothing breaks.
Follow consistent naming conventions – Good naming makes a big difference in code clarity.
Work with refactoring tools – They can save time and help catch issues early.

Examples of these tools:

IntelliJ IDEA
SonarLint
Visual Studio
ReSharper
Eclipse IDE

Conclusion:

Code refactoring may not get the spotlight like flashy new features, but it’s one of the best investments you can make in your codebase. Clean code is faster to work with, easier to test, and way less stressful to debug.

So the next time you touch a confusing piece of code, don’t ignore it. Spend those extra few minutes to refactor it’s a gift to your future self (and your teammates).

One final thought: writing code is easy, but maintaining it is the real challenge. Your code needs to be clean so that your teammates, someone else, or even you, months later, can understand it clearly. So always keep refactoring in mind.

Some of the other Useful blogs for your reference:

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FAQs:
1. Does refactoring mean rewriting code?
  
  Nope! Refactoring improves existing code, not rewrites it from scratch. The goal is to restructure the code internally without changing its external behavior. It helps make the codebase easier to read, maintain, and extend over time.
2. Will refactoring break my code?
  
  Not if you test properly. Refactor step by step and test as you go. Using automated tests gives you confidence that your changes haven’t introduced new bugs. A well-tested codebase makes refactoring much safer and faster.
3. Can I refactor without tests?
  
  It’s risky. Tests help ensure your code still works after changes. If you don’t have tests, add them first or use tools like Keploy to generate tests automatically. Without tests, even small changes can have unintended consequences that go unnoticed.
4. What’s the golden rule of refactoring?
  
  If something is hard to understand or painful to work with clean it up! Good code should be readable and predictable. Refactoring is a discipline that helps maintain the health of your codebase as it grows.
5. What’s the difference between refactoring and optimization?
  
  Refactoring makes code cleaner and easier to work with. Optimization makes it faster or more efficient. You typically refactor to improve maintainability, and optimize to improve performance and both should preserve correct functionality.

Author

Achanandhi M

Developer Advocate at Keploy, writing about cloud-native technologies, CNCF, testing, and GenAI.Outside of tech, you'll find me on the badminton court or with a book in hand. I’m an athlete at heart, and some of my favorites books are "The Alchemist" and "Think Like a Monk" — both inspiring me to push my limits and stay curious. Always up for a chat about tech, community building, or a good book! 😊