What is Regression Testing? A Complete Guide for Beginners

When adding new features or fixing bugs, there’s always a risk of breaking existing functionality. To avoid such problems, regression testing is essential. Regression testing is the process of re-testing software after code updates to ensure that existing features still work as intended. In the tech space, functionality is crucial to maintaining software quality. While constant updates like patches and optimizations are the norm, they mustn’t break existing features. The slightest oversight can lead to significant issues and tech fails, which is why regression testing is essential in preventing such breakdowns.

Think of it as a quality control check for your software. By catching and reporting bugs early and ensuring smooth functionality, regression testing provides confidence that new updates won’t introduce new problems.

Okay, so now that you have an idea of what regression testing is, let’s dive into more technical matters—why is it important, when should you perform regression testing, what are the different types, and what does the testing process look like? Let’s begin.

Why is regression testing important?

Regression testing is essential because it ensures that recent code changes don’t introduce new issues or disrupt existing functionality. This type of testing plays a key role in maintaining software quality, especially in dynamic and evolving projects. Essentially, regression testing is like having a safety net for your software. Here are several key reasons why this type of software testing is crucial.

To avoid unexpected bugs

Imagine spending months building a complex app. It's working smoothly, and then you release a new update. Suddenly, users start complaining that their old favorite feature is broken. These issues can result in negative reviews, customer loss, and damage to your brand's reputation. Regression testing helps prevent these kinds of surprises.

To maintain software quality

Regularly checking that everything is working as it should ensures that new features don’t interfere with existing ones, which means maintaining a high level of software quality.

To ensure functionality of existing features alongside new ones

When you add new features to your software, it's like adding a new piece to a puzzle. You want it to fit seamlessly without messing up the rest of the picture. Regression testing makes sure that your new features integrate smoothly without disrupting other parts of the software.

When should you perform regression testing?

Regression testing should be performed whenever changes are made to the code so that new updates don’t interfere with existing functionality. Here are specific scenarios where regression testing is especially critical:

• After code updates or bug fixes. Timing is everything in regression testing. The most common triggers are code updates or fixes. Anytime a developer makes a tweak, no matter how small, regression testing ensures that the change doesn’t disrupt existing functionality.
• During system integrations. This is another critical moment. When multiple components or third-party systems are integrated, there's a risk that combining them may lead to new bugs. For example, integrating a new payment gateway into an e-commerce platform might cause unexpected issues with order processing.
• Before and after major system upgrades. Regression testing is essential for major system upgrades. Think of large-scale migrations or version updates—when a company shifts from one tech stack to another or introduces a new backend system. During these high-stakes moments, a full sweep of regression testing ensures stability across the entire software, preventing any breakdowns during critical transitions.

Regression testing serves as a constant checkpoint to maintain functionality even with frequent updates. This is why keeping track of bugs is paramount for developers to proceed without breaking existing features.

What are the different types of regression testing?

There are different approaches to regression testing, each tailored to specific needs depending on the scope of changes made.

Unit regression testing 

This type of regression testing focuses on individual units or components of the software. It’s typically done in isolation, where only the modified unit is tested, making sure the update doesn’t introduce new bugs in that specific area. It's a great way to catch bugs early in the development process.

You may also be interested in: Unit Testing: An Introduction.

Partial regression testing 

In partial regression testing, both the changed parts and some related modules are tested to ensure that interconnected functionalities aren’t impacted. For instance, if you modify the login module of an app, partial regression testing will also check related features, like password recovery, to see if everything works as expected.

Complete regression testing

This is the most comprehensive type of regression testing, where the entire system is retested. It’s usually done after major updates or overhauls to confirm that the software as a whole continues to function as expected. While resource-intensive, it is essential for large-scale applications where even minor disruptions can have significant consequences and affect millions of users. For instance, after a major update to an e-commerce platform’s backend, complete regression testing ensures that the checkout, payment, and user account systems work smoothly.

Selective regression testing

Selective regression testing tests a selected subset of test cases based on the changes made to the code. This type focuses on critical areas that are most likely to be impacted. For example, after a bug fix in the checkout process, the testing team would only run tests related to the checkout functionality.

Progressive regression testing

Progressive regression testing is conducted when new features are added. Its purpose is to ensure that both new and existing functionalities work seamlessly together. For instance, if a new payment method is introduced, the team tests it alongside existing methods to confirm compatibility and smooth integration.

Corrective regression testing

This type of regression testing is performed when fixes are made to address bugs to verify that the fixes are effective and do not introduce new issues elsewhere in the application. For instance, after fixing a security vulnerability, other parts of the system must be tested to verify they are unaffected by the change.

However, when time and resources are limited, the most preferred regression testing method is risk-based testing. This approach involves running only high priority tests and tests that are most critical. By using the appropriate type of regression testing at the right time, teams can balance thoroughness with efficiency, making sure their software runs smoothly after any update.

What does the regression testing process look like?

Here’s a breakdown of the regression testing process:

1. Identify and select test cases

• Identify test scope. Determine the most critical functionalities or modules likely to be affected by recent changes. This involves analyzing the nature of the updates and their potential impact on existing features.
• Select existing test cases. Choose relevant test cases from your existing test suites.
• Create new test cases. If necessary, create new test cases to address specific scenarios that might not be covered by existing ones. This ensures comprehensive testing of the updated areas.
• Create a test suite. Create a test suite based on the selected existing test cases and created ones.
• Prioritize test cases. Evaluate the potential risks associated with the changes and prioritize test cases within the suite accordingly. High-risk areas should receive more attention to minimize the likelihood of introducing defects.
• Introduce sanity checklists. Validate the core functionalities of the system in a quick and effective manner.

2. Execute regression tests

• Prepare the test environment. Check whether the test environment is properly configured to accurately reflect the production environment. This helps minimize discrepancies between testing and real-world usage.
• Execute test cases. Follow the established test cases to verify that the updated functionality behaves as expected. Document any deviations or unexpected results.
• Conduct exploratory testing. Conduct exploratory testing to uncover hidden issues or areas that might not be fully covered by the test cases. This can provide valuable insights and enhance the overall testing process.

3. Analyze results and report issues

• Compare results. Compare the actual test results with the expected outcomes. Identify any discrepancies or failures.
• Investigate root causes. Investigate the root causes of any failed tests. Compare between browsers, platforms and versions. Determine whether the issues are related to the recent changes or other factors.
• Document defect. Document and track identified defects in a defect tracking system, providing clear descriptions, reproducibility rate, steps to reproduce, and actual and expected behavior.
• Prioritize defects. Assign priorities to defects based on their severity and impact on the application. This helps guide the development team's efforts and ensures that critical issues are addressed promptly. Regression defects introduced by the latest changes should always be flagged with the highest priority and communicated urgently.
• Communicate issues. Communicate the identified defects to the development team in a timely manner, providing clear explanations and supporting evidence.

4. Re-test after fix

• Re-test affected areas. Once the development team has addressed the identified defects, retest the affected areas to verify that the issues have been resolved.
• Re-run regression suite. Re-run the regression test suite to ensure that the fixes have not introduced any new defects.

5. Update the test suite

• Review and update test suite. Regularly review and update the regression test suite to reflect changes in the application's functionality. This ensures that the suite remains relevant and effective over time.
• Add new test cases. Add new test cases to cover any newly introduced features or modified functionalities. This helps maintain comprehensive test coverage and prevent future regression defects.

By following these steps and paying attention to detail, you can effectively conduct regression testing to ensure the quality and reliability of your application.

Manual vs. automated regression testing

Regression testing can be approached in two main ways: manual and automated. Each has its strengths and is suited for different scenarios. Manual testing involves human testers executing test cases, ideal for exploring complex and user-facing features. On the other hand, automated testing uses scripts and tools to repeatedly execute tests, offering speed and consistency, particularly for large-scale systems.

Choosing between manual and automated regression testing depends on factors like the complexity of your project, the frequency of updates, and the availability of resources. The best approach often involves a blend of both, balancing flexibility with efficiency.

Here’s a comparison of the two methods to help you decide which is best suited for your testing needs:

By leveraging both manual and automated approaches, teams can balance flexibility with speed, ensuring high-quality software without bottlenecks. 

What are the main challenges of regression testing?

Regression testing, while crucial for maintaining software quality, can present several challenges. Here are some common hurdles that testing teams may face:

Challenge #1: Time-consuming process in large systems 

As software systems grow in size and complexity, regression testing can become a time-consuming task. It's essential to find ways to optimize the process and prioritize testing efforts.

Challenge #2: Efficient test management 

Managing a large number of test cases can be overwhelming. Using effective test management tools and techniques will help you stay organized and efficient.

Challenge #3: Prioritizing critical areas for testing 

Not all areas of your software are equally important. For instance, critical features like payment gateways, user authentication, or data security need to be thoroughly tested. Selective retesting might miss bugs in non-prioritized areas, so it's crucial to carefully assess which areas are most likely to be impacted by code changes. Balancing this prioritization with risk is key to efficient regression testing without overlooking potential issues.

Challenge #4: Frequent changes in requirements specification

As a result of constant requirement changes, not only is the code affected, but so are the test cases and their expected results. Keeping the regression suite flexible and easily adaptable to changes is key when dealing with such business practices.

What are some best practices for regression testing?

Here are some best practices for effective regression testing:

• Automate where possible. Automate repetitive test cases to reduce manual effort and speed up the testing process.
• Prioritize test cases. Focus on testing critical areas that are most likely to be affected by changes.
• Use effective test case management tools. Employ tools to organize, manage, and track your test cases.
• Regularly review and update test cases. As your software evolves, review and update your test cases to ensure they remain relevant and effective.
• Leverage test data management. Use tools to manage and generate test data, ensuring that your tests are comprehensive and representative.
• Consider continuous testing. Integrate regression testing into your development process to catch issues early and reduce the cost of fixing them later.

The bottom line

Regression testing is a crucial part of software development. Whether you’re fixing bugs, integrating new features, or rolling out major system upgrades, regression testing ensures that the software remains reliable, consistent, and free from unexpected bugs. By regularly testing the software after changes, you can maintain high-quality standards and deliver a positive user experience. 

Before getting started with regression testing, make sure you recognize the importance of regression testing, familiarize yourself with the different types, and understand the overall process. Additionally, being aware of potential challenges and best practices will help you navigate testing more effectively. 

By following our guide to regression testing, you can effectively incorporate regression testing into your software development process and deliver high-quality, reliable products.

Don't let new features or bug fixes compromise the user experience of your existing software. Reach out today to ensure a reliable product using our expert regression testing services.