[SURVEY RESULTS] The 2024 edition of State of Software Modernization market report is published!
GET IT here

How Red Green Refactor Helps to Modernize Legacy Systems

Last updated on
April 30, 2024



How Red Green Refactor Helps to Modernize Legacy Systems


Legacy systems are often cornerstones of a brand’s operations. However, they can also be viewed as a burden. Their importance for business is undeniable, but their slow performance and outdated features can compromise reliability and reputation. That’s when modernization and migration enter the stage - but how to perform them without experiencing data corruption or loss? Introducing various comprehensive testing methods can be the key to ensuring data consistency, quality, and availability during and after the modernization process.

This article is dedicated to one of the testing approaches used in legacy software modernization - Red Green Refactor. Our goal is to showcase this framework’s characteristics and how it can contribute to risk mitigation and successful system migration. It can be one of the essential factors that can ensure minimized disruptions and help companies go through the stressful process of updating their digital environments with confidence.

What is Red Green Refactor?

Red Green Refactor embodies the principles of test-driven development (TDD), which focuses on writing tests prior to design and development of software elements. Here are the three rules of TDD formulated by Robert Cecil Martin (also known as Uncle Bob), an American programmer and author of multiple books on code writing:

  1. You are not allowed to write any production code unless it is to make a failing unit test pass.
  2. You are not allowed to write any more of a unit test than is sufficient to fail; and compilation failures are failures.
  3. You are not allowed to write any more production code than is sufficient to pass the one failing unit test.

These principles underline the iterative and detailed nature of TDD and Red Green Refactor. The latter focuses on predictability and is made out of three phases that developers should follow to achieve assumed results and excellent quality:

  • Red phase: In the beginning, the programmers write failing tests that should articulate the desired behavior of the code. In other words, the developers have to establish how particular features have to work, which contributes to the process of scope definition and helps to clearly state expectations for the refactoring effort.
  • Green phase: When failing tests are prepared, the involved team members proceed to write the minimum amount of code necessary to pass them. This part of their work is dedicated to aligning the code with specific requirements. When the tests are passed, it means that the written code demonstrates functional integrity.
  • Refactor phase: After finishing the Green phase, it’s time to improve the structure, readability, and efficiency of the code without changing its functionalities. This stage’s key objectives include ensuring maintainability, scalability, and resiliency of the code in the long run.

Benefits of Red Green Refactor

The path to legacy code modernization is fraught with risks, particularly concerning potential downtimes and disruptions. Any data corruption or prolonged period when software is unavailable to the users can have severe repercussions on business operations, brand reputation, and customer trust. Like Jack Godau, CDO at Doctorly, says in our State of Software Modernization 2024 report: “Outages are not possible. There can be no critical disruption to service, which means testing, planning, testing, planning, and repeating until we're certain.

In this context, the Red Green Refactor emerges as a systematic and reliable methodology that allows IT teams to work on legacy software in a more careful manner. What are the other advantages of this testing framework to keep in mind?

  • Safety net: Red Green Refactor is a great method to avoid unintended consequences of modernization. Establishing multiple failing tests upfront allows programmers to quickly identify and address any unexpected behaviors in the code, minimizing numerous risks.
  • Predictable progression: The iterative nature of Red Green Refactor increases the possibility to accurately forecast refactoring outcomes. Teams can create clear and concise roadmaps to follow, with milestones that enable progress tracking and reporting.
  • Continuous quality assurance: Tests integrated into the software migration and modernization workflow help organizations ensure constant levels of quality and integrity within their codebase. Thanks to such frameworks as continuous integration and continuous deployment (CI/CD), developers can facilitate the seamless execution of tests, as well as detect bugs and regressions early on.
  • Adaptability: The development lifecycle in Red Green Refactor allows the introduction of changes with each iteration. Since business requirements can evolve month-to-month, addition of new features is necessary to stay afloat. Programmers can confidently write new pieces of code knowing that the tests will cover their validation.
  • Reduced technical debt: Legacy systems often accumulate technical debt over time. This results in slow performance, but also in hard-to-read code. Red Green Refactor is a great method of addressing tech debt, reducing the complexity of code, improving the quality of the system architecture, and minimizing future maintenance costs.

Are there any challenges in Red Green Refactor pipeline?

Of course, as any methodology, Red Green Refactor is not without drawbacks and challenges. However, if approached with awareness and proper remedies, they can be minimized. For example, this type of refactoring requires a cultural shift within the organization, especially if the hired teams are used to traditional development methods. Investing in training or hiring an external team experienced in such frameworks can be essential for successful implementation.

62.5% of respondents in our State of Software Modernization 2024 report stated that accumulated technical debt and intertwined dependencies are the biggest struggle in software modernization. Changes might seem to be too difficult and risky to introduce, even with the help of Red Green Refactor. That’s why it’s so important to strategize the process. Untangling complex dependencies, eliminating redundant code, and building new parts of the architecture require time and should be done step-by-step.

Another problem companies might stumble upon when trying to introduce the Red Green Refactor methodology as a part of their software modernization efforts is ineffective resource allocation. To plan time, budget, and workforce, they should prioritize each activity in accordance with its business impact and ROI, balancing short-term objectives with long-term goals. This way, they can increase productivity in the project without overwhelming developers with work and also without missing crucial deadlines.

Learn how to build a refactoring strategy and succeed in the competitive, rapidly-transforming digital space.

Best practices for implementing red green refactor

Maximizing the positive impact of introducing Red Green Refactor requires organizations to follow the state-of-the-art practices. What do we recommend?

Start small

In the beginning, identify small, isolated components of the legacy system that could benefit the most from refactoring. Focus on areas that are the most crucial for business or the ones that have to be changed most often.

Iterate often

Plan short, continuous iterations that incorporate feedback from stakeholders and lessons learned from the team. This will not only improve the general process with time but will also enable all interested parties to actively participate in software modernization efforts.

Invest in testing infrastructure

Red Green Refactor shouldn’t be used as a standalone method. Establishing a robust testing infrastructure, which will include manual and automated types of tests necessary to prove your software’s quality (unit, integration, end-to-end tests, etc.), is imperative. This way, companies can streamline the whole QA process for comprehensive coverage, timely feedback, and quicker project progress.

Bet on cross-functional collaboration

Developers, testers, designers, project managers, and other involved stakeholders should work together towards common goals. Open communication, agility, knowledge sharing, and constant improvement should be the guidelines that everyone in the team follows. The same goes for ownership and accountability.

Modernize your legacy system with Red Green Refactor

It seems that Red Green Refactor is a great approach for brands that want to improve their redundant software. However, not every IT department knows this method, and often they are too busy with the current digital presence of the company to handle the demanding modernization process. That’s why it’s so important to find a trusted partner with experience in software migration, modern testing methods, and comprehensive coverage of all required activities.

We can help you with your refactoring strategy and become the provider that will take care of your outdated system without major disruptions and breaks in its existence. Reach out to us and let’s discuss what our team of seasoned experts can do for you and how incorporating Red Green Refactor in your modernization strategy can take it to the next level.

Frequently Asked Questions

No items found.

Our promise

Every year, Brainhub helps 750,000+ founders, leaders and software engineers make smart tech decisions. We earn that trust by openly sharing our insights based on practical software engineering experience.


Olga Gierszal
IT Outsourcing Market Analyst & Software Engineering Editor

Software development enthusiast with 6 years of professional experience in the tech industry. Experienced in outsourcing and nearshoring market analysis. Our expert in presenting tech, business, and digital topics in an accessible way.

Leszek Knoll
CEO (Chief Engineering Officer)

With over 12 years of professional experience in the tech industry. Technology passionate, geek, and the co-founder of Brainhub. Combines his tech expertise with business knowledge.

Read next

No items found...

Get smarter in engineering and leadership in less than 60 seconds.

Join 300+ founders and engineering leaders, and get a weekly newsletter that takes our CEO 5-6 hours to prepare.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

previous article in this collection

It's the first one.

next article in this collection

It's the last one.