Testing Legacy Code: Safe Refactoring

Legacy code is source code acquired from someone else or inherited from an older version of the software. It can also be some code that you don’t recognize and that’s difficult to modify.

Why Is Legacy Code a Challenge?

The biggest difficulty with working with older or unfamiliar code perhaps your assumptions about it. You may think the code is corrupt. Whoever wrote it didn’t understand what they were doing. You could have done a more satisfying job.

But the truth is, there’s normally is a reason why the code is how it is. And, if you didn’t write it, you might not understand that reason. That’s why attention needs to be taken when making improvements to the codebase. You can’t just put a smart fix on one area. There might be some dependencies you don’t know of.

Refactoring legacy code

It’s better to try refactoring legacy rather than rewrite it. And, it’s best to do it constantly.

Refactoring is the method of changing the structure of the code without modifying its functionality. This cleans the code and makes it simpler to understand. It also eliminates possible errors. When refactoring code, it’s best to:

• Refactor code that has unit tests so you know what you have.
• Begin with the deepest point of your code, it will be easiest to refactor.
• Test after refactoring, to ensure you didn’t break anything.
• Have a safety net, e.g., Continuous Integration, so you can return to a previous build.

Tools for Working With Legacy Code

You’ll always need to work with inherited code or work around it. After all, the code is there for a purpose. It works. And its results may be good enough that you can let known issues go. There are good reasons for performing changes to code, too. You might be combining a feature, fixing a bug, or improving the design.

In a perfect world, you’d constantly rewrite that older or unfamiliar code until it’s completely debugged. But chances are, that won’t be possible. So, what you need to do is figure out what you can improve and leave the rest alone.

Static Code Analysis

One way to do this is by utilizing a static code analysis tool. You can establish a baseline and then run an analysis on the new code to ensure it’s clean. And you can overcome results from your codebase. Helix QAC, for instance, makes this very simple to do.

Analyze Legacy Code

Helix QAC can review your codebase against rules, typically from a coding pattern. You’ll get diagnostics of demolitions. And you can prioritize them by severity. This implies you can direct your attention to fixing the most error-riddled pieces first.

Set Baselines

You can also fix your codebase as a baseline. Perhaps the code is fine as-is, and you want to leave it alone. Establishing a baseline means that the codebase won’t be drawn into your diagnostics. Instead, you can concentrate on discovering issues in new code and making sure that’s clean. 

Use Suppressions

You can also use suppressions to generate exceptions for your codebase. So, you can essentially remove violations in it. You might fix your suppressions on particular rules or violations within a particular category.

Ensure Compliance

In some cases, you may be reusing source code from one project to another. But, some weren’t developed with coding criteria. And if you need to accomplish compliance (such as with MISRA), this can generate problems. By using a Perforce static code analyzer, like Helix QAC for C/C++ or Klocwork for C, C++, C#, and Java, it’s simple to see where the mistakes in your code are.

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Testunity is a SaaS-based technology platform driven by a vast community of testers & QAs spread around the world, powered by technology & testing experts to create the dedicated testing hub. Which is capable of providing almost all kind of testing services for almost all the platforms exists in software word.