Effective Strategies for Initiating Testing in a Legacy Codebase

Effective Strategies for Initiating Testing in a Legacy Codebase

3 July 2024 Stephan Petzl Leave a comment QA

Legacy codebases can be challenging to manage, especially when they lack proper testing frameworks and documentation. If you’re tasked with improving the quality of a large, unstructured codebase, it can be daunting to decide where to start. This guide aims to provide a structured approach to initiating testing in such environments, drawing on practical advice from experienced developers.

Deciding Where to Start

When you’re dealing with a large and complex codebase, the first step is to identify the areas that will provide the most value to the business. Here are some strategies to help you get started:

Business Priorities

  • Focus on Business-Critical Areas: Identify the modules or functionalities that are most important to the business. These are the areas where improvement will have the most significant impact.
  • Metrics Collection: Gather metrics before you start and continue to collect them as you progress. Automation can help keep these metrics current, serving as a constant guide and justification for your work.

Static and Dynamic Analysis

  • Static Analysis: Use tools like sloccount, lint, and complexity analyzers to identify problematic areas in the code. Look for high defect rates, above-average complexity, and high dependency modules.
  • Dynamic Analysis: Check which subroutines are most commonly called by examining log files or using code coverage tools. Testing these will likely have a higher impact.

Unit Testing vs. Automated GUI/CUI Testing

In legacy codebases, writing unit tests may be nearly impossible without major refactoring. Here are some considerations:

Unit Testing

  • Unit testing provides deep insights into the code but requires significant effort to refactor and remove dependencies.
  • If refactoring is feasible, tools like OEUnit (a unit testing framework for OpenEdge) can be beneficial.

Automated GUI/CUI Testing

  • Automated front-end tests are directly relevant to the end-user experience and can be developed without affecting the core engineering team.
  • These tests are often easier to implement and can provide immediate value by catching user-facing issues.

Developing a Testing Strategy

Once you’ve identified the areas to focus on and the type of tests to implement, it’s crucial to develop a comprehensive testing strategy. Here are some steps:


  • Rank Modules: Develop an analysis that ranks modules based on their importance to the business, defect rates, design quality, and number of dependencies.
  • Start Small: Begin with a basic test to move from zero tests to an incomplete set that can be improved upon.


  • Automate Builds: Ensure that your build process is automated and integrates with your source control system.
  • Incremental Testing: Write one test at a time, starting with simple tests and gradually increasing complexity.


Initiating testing in a legacy codebase is a challenging but rewarding endeavor. By prioritizing business-critical areas, leveraging static and dynamic analysis tools, and developing a comprehensive testing strategy, you can significantly improve the quality and maintainability of your codebase.

For those looking to streamline their testing processes without extensive coding, consider using tools like Repeato. Repeato is a no-code test automation tool for iOS and Android that leverages computer vision and AI to create, run, and maintain automated tests quickly and efficiently. It’s particularly useful for quality assurance teams looking to implement automated testing without the need for extensive coding knowledge.

Like this article? there’s more where that came from!