Software Regression Testing: Understanding the Basics
Another type of software testing, regression testing is a critical component of ongoing development to make sure that new fixes don’t break other areas of your application. Keep reading to get a better understanding of what regression testing is, how it differs from other similar methods, and how to successfully execute it in your projects.
What is Regression Testing?
Regression testing is a technique often used after changes are made to a software product to verify that the new additions or tweaks haven’t negatively affected functionality (or resulted in the product “regressing”). If you read our article explaining sanity testing, this might sound familiar. However, sanity testing performs these checks on narrow areas after minor code changes, while regression testing evaluates larger swathes of the application after more significant changes.
Regression testing typically re-uses test cases from previous cycles to confirm that the already-established functionality still works as expected. There are some instances where manual processes are used for regression testing, but the vast majority of it is automated for efficiency. To put it simply, having to test an entire application after every code merge, bug fix, or feature addition results in most sane developers leaning on automation.
Why is it Important?
The obvious importance of regression testing comes from the verification of functionality after a significant change to the code. However, it also provides other benefits and reasons to incorporate into your processes. For one, the ongoing checks build more confidence in the quality of each release, minimizing end users running into major issues. It also saves time and money in the long run, because of the often exponential increase in cost to fixing a bug the longer it goes unnoticed.
Additionally, for DevOps and Agile teams, it fits nicely with iterative development and frequent deployment, providing rapid feedback on changes without delaying timelines. All of these make regression testing a valuable item in your toolbox, especially for modern application lifecycles that are often compressed to get updates out to users more quickly.
Regression Testing Example
To get a better understanding of what this would look like in practice, let’s take an example of an e-commerce shopping platform. The dev team recently added a new feature that enables users to filter products by price range to more easily find what they’re looking for.
The first step of regression testing is to identify the affected areas — in this case, it would be the product listing page that shows all products, which is where the filter was added. The filter could potentially affect things like:
- Sorting options (by price, by popularity, etc.)
- Search functionality
- Pagination of product listings
- Add-to-cart functionality from the listing page
Note: For reference, sanity testing might just check one of these items, while regression testing verifies that all of these work to ensure the entire listing page functions properly.
From there, we can identify the existing test cases that relate to these features, for use in regression testing. This might include:
- Test case that evaluates whether sorting options behave as expected
- Test case that verifies the search bar shows relevant products based on user input
- Test case that ensures pagination works correctly across listings
- Test case that confirms the “add to cart” button still functions correctly from the listing page
From there, our fictional development team would run these test cases again with the new filter to validate their functionality. Analyzing the results is the final step, where an issue might pop up — such as the sorting by ascending price not working with a price range selected. From there, the developers can find the source of the bug, fix it, and re-run the affected test case to make sure it’s resolved.
Regression Tools
But how do we run all of these automated tests and manage them? Modern automated software testing tools like Selenium, Cypress, and Rapise often include regression testing functionality. The specifics of each will vary, so look for a tool that offers a relatively intuitive interface without sacrificing functionality or feature depth.
Smoke Testing vs. Regression Testing
We mentioned the similarities between regression and sanity testing earlier, but other types of tests can be confused with regression as well. One of these is smoke testing, which confirms that the application’s critical functionalities work. This typically has a narrower focus than regression testing and is meant to check if the current build is even stable enough for further testing. One of the other key differences is that smoke testing is usually performed on a deployed build and performed manually, while regression testing is automated.
Unit Testing vs. Regression Testing
Unit testing (as the name might suggest) is much smaller scale than most forms of regression testing and is contained to assessing a single unit of new code. For example, this might test the new function that calculates your total price in the cart, compared to larger-scale regression testing that might look at the entire (existing) checkout process.
Integration Testing vs. Regression Testing
Typically done after unit testing, integration testing verifies that different components work together correctly, but doesn’t extend beyond these interactions between modules. On the other hand, regression testing again takes a more holistic look at the application and uses existing test cases from these previous testing cycles to make sure the whole product works.
Regression Testing Types & Techniques
There are several different subsets and techniques within regression testing, each of which has strengths and weaknesses that make them preferred for certain situations.
Corrective
Corrective regression testing is used when no major changes have been made to the code, but re-testing needs to be performed to make sure everything still works correctly. A development team might opt for this kind of testing after a minor bug fix or update is implemented. For example, fixing a typo in a UI label and re-testing to check that it displays correctly without affecting other features.
Retest-All
Retest-all regression testing involves (as you might guess) re-testing the entire application to confirm that recent changes haven’t caused issues anywhere across the system. This includes all test cases, no matter how relevant or low-risk. Because of the scale of this and how time-consuming it can be, it’s usually reserved for after major changes. An instance where retest-all might be used is after overhauling the database structure, ensuring that system-wide functionality is still working as expected.
Complete
Complete regression testing dives deep into the application to re-test the entire system, including both new and old features. This typically prioritizes high-risk areas and is reserved for the preparation of major releases or deployment to production. While similar to retest-all regression testing, complete regression testing uses risk analysis to focus testing efforts on the most important areas and core functionality, making it more efficient.
Selective
Similar to sanity testing, selective regression testing hones in on specific parts of the application that were affected by code changes (and doesn’t test unaffected areas). This saves time and resources when full-scale testing isn’t necessary, such as our product listing page example above — we thoroughly test a specific area (the product listing page), but not the entire website.
Partial
A slightly narrower version of selective regression testing, partial regression testing evaluates the modified features and their direct dependencies. However, it doesn’t extend to indirect connections and features that might be affected. Because of this, partial is used when changes are known to be localized and contained, without risk of affecting other nearby functionalities (in which case, selective would be better).
Progressive
If additional test cases are created for new functionality, progressive regression testing is used to validate them while ensuring that previous functionalities still work. This kind of testing is most common in iterative development like Agile environments. For example, if a new shipping option is added, progressive regression testing might be used to verify that the old shipping methods still work without issue.
Unit
Lastly, unit regression testing takes traditional unit testing discussed above but uses the timing of regression testing (after a change is made). In other words, it revolves around testing an existing individual unit of code after it’s been recently modified to verify that its functionality hasn’t regressed. This is in contrast to traditional unit testing that analyzes new pieces of code for correctness.
Challenges of Regression Testing
Unfortunately, regression testing isn’t ideal in all development scenarios — for example, large codebases can cause exponentially increasing time to test because of the volume of associated test cases. This is where methods that prioritize test cases (like complete or partial regression testing) can be valuable, preventing testing scope from getting out of control. Automation is another huge help in mitigating this hurdle.
Another challenge of regression testing is that automation can be costly for smaller teams due to the complex systems powering it. However, some platforms like Rapise have adjustable pricing that scales to your needs, tailoring the plan you get to your actual requirements. While automation makes the process faster, repeated testing after every significant change does inevitably slow down releases compared to more limited testing — but this is the price of better quality assurance.
Best Practices
To overcome pitfalls and maximize the value of your regression testing we recommend the following practices and habits:
- Prioritize Critical Areas: Remember that not all units or parts are equally vulnerable to regressions (or have the same impact), so focus on testing the most risky and consequential areas.
- Maintain a Well-Organized Test Suite: Cluttered and redundant test documentation wastes your time and resources on low-value validations, so use a dedicated test management tool to organize this and maintain traceability.
- Automate, Automate, Automate: We’ve already covered how most regression testing is done via automation because of its repetitive nature, so look for an automated testing tool that can handle all this and more to upgrade your suite of tools at the same time.
- Make Use of Version Control: This feature can help identify areas affected by recent code changes and facilitate a more targeted approach to regression testing, saving time and money.
- Keep Test Cases Up-to-Date: Outdated test cases can cause false positives, false negatives, or missed defects when used in regression testing, so ensure they’re kept relevant and reflect the evolving requirements of your project.
- Incorporate Different Methods: The types of regression tests we mentioned above are better and worse in different situations, so make use of all of them — from unit to complete testing.
When to Use a Regression Test
Now that we know how to regression test, let’s circle back for a refresher on when to regression test. It’s best for after code changes (adding a new feature, fixing bugs, refactoring code, etc.), during maintenance or updates (migrating to new platforms, updating libraries or APIs, improving performance, etc.), and in Agile or DevOps workflows (frequent builds and deployments). These environments are generally thought of as the “best” situations for regression testing, but that doesn’t mean it can’t be used elsewhere!
Test Your Software More Effectively
Ensuring that your testing is both comprehensive and efficient is critical to keeping software projects on schedule and under budget. This relies not just on understanding best practices and when to use a given test type, but also on having the right tools. Rapise is the industry-leading solution for automated testing across a variety of techniques, platforms, frameworks, and more. Not only does it have some of the most powerful capabilities out there, but balances this with an intuitive interface and price flexibility — your team of 10 shouldn’t be locked into a 3-year license built for a team of 50. Explore the highlights of Rapise or hear from our partners on why it’s an indispensable tool for quality assurance and streamlining processes.