How to Debug Code You Did Not Write

As a software engineer, it is inevitable that at some point you will be tasked with debugging code that is not your own. This can be a daunting challenge, but with the right approach, you can tackle these issues effectively. In this article, we will explore a systematic method for debugging code you didn't write, as well as some tips for debugging code you did write.

Debugging Code You Did Not Write

The process of debugging code you did not write can be challenging, but it is crucial for maintaining and improving software.

1. Duplicate the Bug

The first step is to duplicate the bug. This can be difficult, and the complexity of the code can make it even more challenging. If you are unable to reproduce the bug, reach out to the original developer for more information. Details about the environment, specific actions leading to the bug, and system logs can be invaluable.

2. Locate the Problematic Code

Once you have duplicated the bug, the next step is to locate the code where the bug is occurring. If the bug is logged, the code location can be easily identified. If not, you will need to start guessing based on your knowledge and experience. You can also seek advice from other software engineers for their insights.

3. Analyze the Code

Set breakpoints and step through the code. Try various inputs or scenarios to dig deeper. Use logs to track the flow of the program and identify where things go wrong. If the issue persists, ask for help or try to deduplicate the issue by running shadow logs or seeking guidance from the original developer.

Debugging Code You Wrote

Debugging code you wrote is often easier because you have a deeper understanding of the code. However, it still requires diligent effort and adherence to best practices.

1. Understand the Code's Purpose

First, learn what the code is supposed to do rather than what it actually does. This involves reading the code and familiarizing yourself with its structure. Understanding the business logic and requirements is crucial.

2. Test the Code Thoroughly

Try various inputs or scenarios to test the code. This helps you identify edge cases and potential issues. Make sure to document the test cases and outcomes.

3. Learn the Environment

It is essential to know how to run and build the code. Sometimes, you may need access to specific servers or unique logins. Leverage any documentation you can find and seek help from more experienced colleagues.

4. Reproduce the Bug

Understand the bug and if it can be reproduced, have confidence in your findings. Try to set up a unit test that reproduces the bug whenever possible. This simplifies the debugging process and ensures that you can consistently test the fix.

5. Use Logging and Debugging Tools

If you cannot use a debugger, use logging to trace the flow of the code and identify where things go wrong. Write out helpful messages like ‘MJB Entering function A’ or ‘MJB Function A lineId: 10’ to track your progress. Notes and logging should be extensive but easily understandable.

Conclusion

Debugging is a skill that requires persistence and a methodical approach. Whether you are debugging code you wrote or did not write, the key is to understand the problem, gather information, and use the right tools to diagnose and fix the issue.