Regression testing - A Detailed Guide
Tags: testing, mobile, webdev, automation
Published: 2024-06-29 06:14:45

In the fast-paced landscape of rapid software development, where upgrades and modifications are frequent, it is crucial to ensure the stability and quality of software products. Regression testing plays a vital role here.

Regression testing is a fundamental testing process that consists of repeated testing of the existing features of any tool, application, or system as it receives new upgrades. Testers conduct regression tests to ensure that an application's live and new functionalities remain working and undamaged. Under this testing approach, the quality analyst checks existing features' functional and non-functional aspects to [ensure no new bugs or errors in the application](https://www.headspin.io/solutions/mobile-app-testing).

Running regression tests is more than just re-running previous test cases; it ensures that new functionality is compatible with the existing ones without breaking the system now or in the future.

## What is regression testing? Why do we need it?

Regression testing is a type of software testing conducted to confirm that a recent change or upgrade in the application has not adversely affected the existing functionalities. A tester initiates a regression test soon after the developer incorporates a new functionality into the application or finishes fixing a current error. Often, when one code module is changed or upgraded, another module is likely to be affected due to dependencies existing between these two.

### Why is regression testing crucial? 
A regression testing approach is required to evaluate the overall working of the application after it has undergone a change for various reasons, including:

- **Identifying regression defects**: Regression tests help detect any unintended defects or issues that may have been introduced during software development or modifications. These tests help examine the functionality of the upgrade. Regression tests ensure that the change does not interfere with the existing features of the software and identifies any errors or bugs in the application's existing functionalities. It also helps determine bugs in the newly pushed code.

- **Ensuring stability**: This form of testing verifies that the existing functionality of the software remains intact after changes are made. It helps detect any unexpected behavior or issues that could impact user experience, ensuring the stability of the software.

- **Mitigating risks**: Through comprehensive regression testing, potential risks associated with changes can be identified and mitigated. It helps prevent unexpected issues, system failures, or performance degradation that could impact business operations or user satisfaction.

![regression testing timeline](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/rtb020efi0y5ggqm49u9.png)

### Example of regression tests
Let's consider a web-based e-commerce application. Suppose the development team adds a new feature that allows users to apply discount codes during checkout. To perform regression testing, the following steps could be taken:

- **Comparison and analysis**: The regression test results are compared against the baseline test results to identify any deviations or discrepancies. Any failures or unexpected behavior are thoroughly investigated and reported as defects to the development team for resolution.
- **Regression test selection**: Test cases related to the impacted areas, such as the checkout process and order calculation, are selected for these tests. These test cases focus on validating that the existing functionality remains intact after the code changes.
- **Baseline testing**: Initially, a set of test cases is executed on the existing version of the application to establish a baseline of expected behavior. This includes testing various functionalities like product browsing, adding products to the cart, and completing the purchase without applying any discount codes.
- **Code changes**: The development team adds a new feature to the application that introduces the ability to apply discount codes during checkout.
- **Test execution**: The selected regression test cases are executed on the modified application to ensure that the new feature works as expected without causing any issues in previously functioning areas.
- **Re-test and confirmation**: Once the identified issues are fixed, the impacted test cases are re-executed to confirm that the fixes are effective and that the previously working functionality has been restored.

## When to use regression testing
Regression testing is crucial at various stages of the SDLC to ensure the stability and functionality of the application. Here are key scenarios when you should perform regression testing:

- **After Code Changes**
When developers add new code or modify existing code, regression testing is essential to verify that these changes haven't adversely affected the application's existing functionality. This includes bug fixes, feature enhancements, or code refactoring.

- **After Integration**
When integrating new modules or components into the application, regression testing ensures that the integration does not introduce new bugs or issues. It helps verify that the integrated components work seamlessly with the existing system.

- **During Major Releases**
Before rolling out major releases or updates, testers must conduct extensive regression testing to ensure the new version does not disrupt existing features and functionalities. This is particularly important for applications with a large user base or critical functionalities.

- **Post Maintenance Activities**
After performing routine maintenance activities, such as updating libraries, frameworks, or other dependencies, regression testing helps ensure that these updates do not negatively impact the application.

- **After Performance Enhancements**
When performance optimizations are made to the application, regression testing verifies that these improvements do not compromise the correctness and reliability of the application. This includes testing for any unintended side effects that might degrade user experience.

- **Before and After Deployments**
Regression testing ensures that deploying new changes will not introduce new issues. Post-deployment regression testing helps identify any problems in the live environment, ensuring quick resolution and minimal impact on users.

- **During Continuous Integration/Continuous Deployment (CI/CD)**
In a CI/CD pipeline, regression testing is an integral part of the process. Automated regression tests run after every code commit to detect issues early in the development cycle, ensuring a stable and reliable application at all times.

By strategically incorporating regression testing in these scenarios, teams can maintain the quality and reliability of their applications, providing a seamless and bug-free experience for users.

> Read: [Smoke Testing vs Regression Testing](https://dev.to/abhayit2000/smoke-testing-vs-regression-testing-understanding-the-key-differences-10bk)

## Strategies to perform regression tests - what to test, how often, and more

Regression testing strategy depends on several key factors, like how often developers upgrade the application, how significant the new change is, and what existing sections it could affect.

Here are some tried and tested proven strategies that you could follow during regression testing:

- The regression testing approach must cover all the possible test cases and impacted functionalities.
- When introducing automation testing, outline the test cases and scenarios to know which should be automated and manually tested.
- Focus on the testing process, technology, and roles when automating regression testing.
- Measure or change the scale of the upgrade to determine how likely it would affect the application.
- Perform risk analysis based on the size of your business/project and its complexity, along with its importance.

## How does one manage regression risks and ensure they don't impact the product release schedule?

The risks associated with regression testing of a software can significantly impact the product release schedule. The following are some tips for managing regression risks:

- Proactively identify and assess regression risks before starting the testing process. You can then focus all your efforts on the most critical areas.
- Use a structured approach for managing regression risks, such as a risk registry or risk management plan; this will help ensure that all threats are captured and tracked.
- Use risk mitigation strategies to reduce the impact of identified risks. For example, if a particular threat could result in data loss, you could create backups to mitigate the risk.
- Communicate any potential impacts of regression risks to stakeholders to make informed decisions about the release schedule.

While regression tests are an essential part of the software development process, they can also be time-consuming and costly. Automating regression tests can help reduce the cost and time consumed for testing while providing high coverage. When deciding whether to automate regression testing, consider the following:

- **The type of application under test**: Automated regression testing may not be feasible for all applications. For example, if the application has a complex user interface, it may be challenging to automate UI-based tests.
- **The frequency of changes**: If the application is subject to frequent changes, automated regression tests can help save time in the long run.
- **The resources available**: Automated regression testing requires a significant upfront investment in time and resources. If the project budget is limited, automating all regression tests may not be possible.
- **The coverage desired**: Automated regression tests can provide high coverage if well-designed. However, manual testing may be necessary to supplement automated tests and achieve 100% coverage.

## How do you perform regression tests on your applications or software products?

In general, there are three steps for performing these tests: 

- **Prepare for manual and automated tests**: This involves getting the required tools and resources ready, such as test data, test cases, test scripts, and more.
- **Identify which changes or upgrades on existing modules of the application will impact its functionalities**: You need to specifically identify which areas of the application will be affected by the changes or upgrades to focus your testing efforts on those areas.
- **Use manual and automated tests accordingly**: Once you have identified the impacted functionalities, you can use both manual and automation tests to validate that the changes or upgrades have not adversely affected those functionalities.

Some of the most common regressions that need testing include functionalities such as login, search, and checkout. To detect these regressions, you can use different methods such as checking the application's output against expected results, performing functional tests, and using automated tools such as HeadSpin.

## Difference between automated regression testing and functional testing
Functional testing and regression testing are two distinct but complementary approaches to software quality assurance. While functional testing focuses on verifying the correctness of individual features, regression testing is concerned with preserving existing functionality after making changes to the code. Both approaches are essential for ensuring that software meets customer expectations and can be deployed safely to production environments.

A crucial part of any continuous integration or delivery pipeline, automated regression testing helps ensure that new code changes do not break existing functionality. By running a suite of automated tests against every build, developers can quickly identify and fix any regressions before reaching production.

While enterprises focus on different aspects of regression testing, it is essential for them to consider the growing agile landscape and how this landscape can impact the testing practices. Quicker ROI and time-to-market, constant app upgrades, and better use of user feedback have all been major benefits ushered by agile, but it is often a challenge to balance agile sprints with iterative practices like regression testing. The following section offers a clearer view of regression testing in the agile scenario.

![Automated regression testing vs Functional testing](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4us2dt4l2xvilml1iw3j.png)

## The Importance of Regression Testing
In the dynamic world of software development, regression testing stands as a cornerstone of quality assurance, ensuring that once operational software continues to perform well after it has been altered or interfaced with new software. Below, we explore why regression testing is indispensable:

**Ensuring Software Stability**
Regression testing is vital for verifying that the existing functionalities of an application continue to operate as expected after any modifications. This could include code changes, updates, or enhancements. The goal is to ensure that the new changes do not introduce any unintended disruptions to the functioning of the software.

**Detecting Bugs Early**
One of the key benefits of regression testing is its ability to identify defects early in the development cycle. This saves time and significantly reduces the cost associated with fixing bugs later in the development process. By catching regressions early, teams can avoid the complexities of digging into deeper layers of code to resolve issues that could have been avoided.

**Facilitating Continuous Improvement**
As software evolves, regression testing ensures that each new release maintains or improves the quality of the user experience. It supports continuous improvement by enabling teams to continuously assess changes' impact, ensuring the software remains robust and reliable.

**Supporting Integration**
In today's tech environment, applications rarely operate in isolation. They often interact with other systems and software. Regression testing verifies that updates or new features work harmoniously within the existing system and with external interfaces without causing disruptions.

**Aiding Scalability**
As applications grow and more features are added, regression testing becomes crucial to ensure enhancements do not compromise the system's scalability. It helps confirm that the system can handle increased loads and scale without issues.

## The Difference Between Regression Testing and Retesting
The terms "regression testing" and "retesting" are often heard in software testing, but they refer to very different processes. Understanding these differences is crucial for effective test planning and execution.

**Retesting**, also known as confirmation testing, is the process of testing specific defects that have been recently fixed. This type of testing is focused and narrow in scope. It is conducted to ensure that the specific issue fixed in a software application no longer exists in the patched version. Retesting is carried out based on defect fixes and is usually planned in the test cases. The main goal is to verify the effectiveness of the specific fix and confirm that the exact issue has been resolved.

On the other hand, **regression testing** is a broader concept. After retesting or any software change, it is performed to confirm that recent program or code changes have not adversely affected existing functionalities. Regression testing is comprehensive; it involves testing the entire application or significant parts to ensure that modifications have not broken or degraded any existing functionality. This type of testing is crucial whenever there are continuous changes and enhancements in an application to maintain system integrity over time.

**Key Differences**:

- **Purpose**: Retesting is done to check whether a specific bug fix works as intended, while regression testing ensures that the recent changes have not created new problems in unchanged areas of the software.
- **Scope**: Retesting has a narrow scope focused only on the particular areas where the fixes were applied, whereas regression testing has a wide scope that covers potentially affected areas of the application beyond the specific fixes.
- **Basis**: Retesting is based on defect fixes, typically done after receiving a defect fix from a developer. Regression testing is based on the areas that might be affected by recent changes, encompassing a larger part of the application.
- **Execution**: Retesting is carried out before regression testing and only on the new builds where defects were fixed, while regression testing can be done multiple times throughout the software lifecycle to verify the application's performance and functionality continually.

Understanding the distinct roles and applications of retesting and regression testing allows quality assurance teams to allocate their resources better and plan their testing phases, ultimately leading to more robust and reliable software delivery.

## Challenges in Regression Testing
Regression testing, an essential part of maintaining and enhancing software quality, faces numerous challenges that complicate development. Understanding these challenges can help teams prepare better strategies and tools to manage them effectively.

- **Time Constraints**
As software projects evolve, the number of test cases needed to cover all features and functionalities grows. Running these comprehensive test suites can become time-consuming, especially in continuous integration environments requiring quick turnarounds. Balancing thorough testing with the demand for rapid development cycles remains a critical challenge.

- **Resource Allocation**
Regression testing often requires significant computational resources to execute many test cases. In addition, human resources are needed to analyze test results, update test cases, and manage the testing process. Efficiently allocating these resources without overspending or overworking team members is a key issue many organizations face.

- **Test Maintenance**
As software is updated or expanded, regression test cases must be reviewed and updated to cover new features and changes. This ongoing maintenance can be burdensome as it requires constant attention to ensure that tests remain relevant and effective. Neglecting test maintenance can lead to outdated tests that no longer reflect software health accurately.

- **Prioritization of Test Cases**
Test cases vary in importance, and frequently running less critical tests can waste valuable time and resources. Determining which test cases are crucial and should be run in every regression cycle versus those that can be run less frequently is a challenge. To solve it, you need a deep understanding of the app and its most critical components.

- **Flaky Tests**
Flaky tests, or tests that exhibit inconsistent results, pose a significant challenge in regression testing. They can lead to teams ignoring important test failures or wasting time investigating false positives. Managing, identifying, and fixing flaky tests require a structured approach and can be resource-intensive.

**Keeping Up with Technological Changes**
Regression testing strategies and tools must evolve as new technologies and development practices are adopted. Staying current with these changes without disrupting existing workflows is an ongoing challenge for testing teams.

## Creating an Effective Regression Test Plan
A regression test plan is a pivotal document that outlines the strategy, objectives, and scope of the regression testing process. It comprises various essential components to ensure an efficient and effective testing procedure.

### Key Goals for the Regression Test Plan
- **Comprehensive Testing**: Encompass all software aspects within the testing framework.
- **Automation of Tests**: Automate tests to enhance efficiency and reliability.
- **Test Maintenance**: Plan for test maintenance to ensure tests remain up-to-date.

### Assumptions and Dependencies
- **Stable Application Version**: Assume the application version is stable with no major architectural overhauls.
- **Real-world Simulation**: Assume the test environment accurately replicates a real-world setup.
- **Availability of Test Cases and Data**: Assume the availability and accuracy of test cases and test data.

Ensure all these assumptions and dependencies are documented for effective collaboration among teams.

## Essential Components of the Regression Test Plan
- **Test Cases**: Define comprehensive test cases based on scenarios and requirements, covering all system functionalities.
- **Test Environment**: Identify necessary hardware and software configurations, including the app version, OS, and database.
- **Test Data**: Develop consistent and diverse test data for various testing scenarios.
- **Test Execution**: Define the test execution schedule, resources required, and regression test timeline.
- **Defect Management**: Establish a process for reporting, tracking, and managing defects, incorporating severity and priority levels.
- **Risk Analysis**: Identify risks associated with regression testing and devise a mitigation plan to manage them.
- **Test Sign-off**: Define criteria for successful test sign-off, including required metrics and results.
- **Documentation**: Prepare comprehensive documentation covering test cases, test data, results, and defect reports.

The regression test plan ensures a robust testing infrastructure and facilitates efficient testing processes by encompassing these key elements.

## Regression testing in Agile 
In the agile context, testing is required to develop with every sprint, and testers need to ensure that the new changes don’t impact the existing functionality of the application. There are numerous and frequent build cycles in agile contexts, along with continuous changes being added to the app, which makes regression testing more critical in the agile landscape. To achieve success in an agile landscape, the testing team must build the regression suite from the onset of the product development and continue developing these alongside development sprints. 

### The key reason for considering regression tests showcase in agile development

In any agile framework, very often, the team focuses on functionality that is planned for the sprint. But when the team pertains to a particular product space, they aren’t expected to consider the risks their changes might lead to in the entire system. This is where regression testing showcases the areas that have been affected by the recent alterations across the codebase. Regression testing in agile seamlessly helps ensure the continuity of business functions with any rapid changes in the software and enables the team to focus on developing new features in the sprint along with overall functionality.

### Creating test plans for regression testing in Agile
There are multiple ways that regression tests have been embraced into agile, which primarily depend on the type of product and the kind of testing it requires. The two common ways of constructing test plans for regression testing in Agile are:

1. **Sprint-level regression testing** - This type of test emphasizes on executing the test cases that have emerged only after the last release.
2. **End-to-end regression testing** - This type of test focuses on covering tests on all core functionalities present in the product.

Based on the level of development and product stability, a suitable approach for test plan creation can be deployed. 

### How can you perform regression testing in an agile scenario?
Agile teams move very fast, and regression suites can thereby become very complex if not executed with the right strategy. In large projects, it is wiser for teams to prioritize regression tests. However, in many cases, teams are compelled to prioritize based on ‘tribal knowledge’ of the product areas, which are more prone to error and are anecdotal evidence from production faults and ineffective metrics like defect density. 

To perform regression tests in agile, it is essential for teams to consider certain critical aspects like:

1. Making it a practice to differentiate sprint-level regression tests from regular regression test cycles.
2. Focusing on choosing advanced automated testing tools that help generate detailed reports and visualizations like graphs on test execution cycles. These reports, in most scenarios, assist in evaluating the total ROI. 
3. Updating regression test scripts on a regular basis to accommodate the frequent changes.
4. Leveraging the continuous changes to the requirements and features driven by agile systems along with changes in test codes for the regression tests.

Categorizing the test cases on the basis of high, medium, and low priorities. End-to-end testing flows effectively at the high-priority test suite, the field level validations at a moderate level, and the UI and content-related tests at a low level. Categorization of test cases enables new testers to quickly grasp the testing approach and offer robust support in accelerating the test execution process. Prioritizing test cases also allows teams to make the process simpler and easier to execute, thereby streamlining the testing process and outcomes.

### Creating regression tests strategy for agile teams
Repeated tests for continually expanding and altering codebases are often time-consuming and prone to errors. As agile development primarily focuses on speed, the sprint cycles are short, and developers often eliminate specific features in each. To avoid any emerging issues, regression testing needs to be effectively strategized and aligned with agile principles and processes. Following are some of the techniques for testing regressions seamlessly in the agile process:

- **Embracing automation** - In order to speed up regression tests for Agile sprints, automation is almost non-negotiable. Teams must begin with automated regression test scripts and then proceed with making alterations with every new feature. Automated regression tests are best suited after the product has been developed to a significant extent. Also, these regression tests should be coupled with certain manual verifications to identify false positives or negatives. 
- **Focusing on severely vulnerable areas of the software** - As developers are well aware of their software, they should narrow down the specific areas/features/functionalities/elements of the product that have high probabilities of getting impacted by the changes in every sprint. Also, user-facing functionalities and integral backend issues should be verified with regular regression tests. A collaborative approach for testing app regressions can be fruitful in helping developers combine the benefits of both testing approaches.
- **Incorporating automation only in specific limits** - However much the test infrastructure is modernized, aiming for complete or 100% automation is not a viable option. Certain tasks like writing test scripts and verifying results by human testers need to be executed for improved testing outcomes. Deploying the right percentage of automation will result in a lesser number of false positives/negatives, which is suitable for identifying regressions in agile. However, with the rising focus on assuring high product quality, implementing the right techniques and proportion of automation in regression testing in an agile environment has enabled teams to guarantee a more stable and reliable product at the end of every sprint each time.

## Different methods of setting up a regression testing framework
When the testing team opts for automated regression testing, they simultaneously must define the test automation framework for the purpose. By defining the test automation framework, testers can give a definite structure to the test cases when they are automated. Here is how a defined architecture plays a vital role in automated testing:

- A designated QA professional, along with their preferred choice of automation testing tool
- A suitable and relevant structure includes test cases and test suites.
- A basic testing script to run the regression tests, which is also scalable and accommodating to the new test cases
- Before developing a test automation framework, QA professionals complete integration tasks to ensure that they can focus solely on running the script for regression testing.

## Best practices for regression testing - tips on improving your process
- Make detailed test case scenarios for regressing the testing approach.
Keep the test case file updated with new scenarios and perform regression tests based on that file.
- Create a standard procedure for regressing testing regularly.
Identify the functionalities or application areas at high risk due to recent upgrades or changes.
- Link these tests with functional as well as non-functional testing.
- Run regression tests after every successful compiling of the new code.
Design the regression tests approach based on the risk factors surrounding the business model for the application.
- Perform desired regression tests action and compare it with the expected/previous response for correctness.
- Integrate automated regression testing into your continuous integration or delivery pipeline; this will help ensure that new code changes do not break existing functionality and that any regressions are quickly identified and fixed.
- Establish a process for the regression tests and ensure that everyone involved in the project is aware of it; this will help ensure that you and your team take the necessary steps to test all changes adequately.
- Identify the changes or upgrades done on existing modules of the application that will impact its functionalities; this will help you focus your testing efforts during regression testing on those areas.
- Use manual and automated tests to validate that the changes or upgrades have not adversely affected functionalities; this will help you catch any regressions that the changes or upgrades may have introduced.

## Types of tests that you can use in a regression framework
There are several types of tests you can conduct using a regression testing framework:

- Re-run previous test cases and compare the results with the earlier outputs to check the application's integrity after code modification
- Conduct regression testing of a software by running only a part of the test suite, which might be affected due to the code change
- Take an approach for testing regressions where you execute test cases priority-wise; you run higher priority cases before lower priority test cases (You can prioritize test cases based on checking the upgraded/subsequent version of the application or the current version.)
- The above two techniques can be combined for hybrid test selection, assessing regressions for a part of the test suite based on its priority.

## Common mistakes when running regressions tests
Developers can make common mistakes that they can prevent with extra care. Here are a few errors that you can avoid making:

- Avoiding conducting regression testing after code release/change or bug fix is a mistake.
- Not defining a framework for testing regressions or not sticking to one will execute arbitrary test cases and suites on any automation tool that would cost time, money, and bug identification.
- Not defining a goal and making it invisible to everyone involved in the project.
- Re-running the same test cases is time-consuming and costly; yet, regression tests is necessary to ensure the application does not break when upgrading it to a newer version.
- Not opting for automation testing over the manual approach.

These are the most common mistakes any professional can make while conducting regression testing. To avoid these, HeadSpin offers an intelligent regression testing approach that includes an automated solution to all your regression issues.

## Tools to perform your software regression testing
These are some of the most famous regression testing tools available today. Each has its strengths and weaknesses, so choosing the right tool for your specific needs is essential.

- **HeadSpin Regression Platform** is a regression testing tool that uses intelligent test automation to test web and mobile applications. HeadSpin designed the platform to help developers quickly identify and fix any regressions before reaching production. HeadSpin Regression Platform integrates with various development tools and supports many browsers and operating systems, making it a versatile option for regression testing.
- **Selenium WebDriver** is a popular open-source tool for web application regression testing. Testers can use it to automate tests against both web and mobile applications. It supports various browsers and operating systems, making it a versatile option for regression tests.
- **JUnit** is a popular open-source unit testing framework for Java development. Testers can also use it for regression testing by creating test cases that exercise the functionality of an application. JUnit is easy to use and integrates various development tools, making it a good option for regression tests.
- **TestNG** is another popular open-source testing framework, similar to JUnit. It also supports regression testing and has good integration with various development tools.
- **Cucumber** is a popular tool for behavior-driven development (BDD). Testers can use it for regression testing by creating test scenarios that exercise the functionality of an application. Cucumber's readable syntax makes it easy to build regression tests that both developers and non-technical stakeholders understand.
- **Appium** is a tool for mobile application regression testing. Testers can use it to automate tests against native, web, and hybrid mobile applications. Appium supports a wide variety of mobile platforms, making it a versatile tool for regression testing.
- **Watir** is a tool for regression [testing of web applications](https://www.headspin.io/blog/a-complete-guide-to-web-app-testing). Testers can use it to automate tests against web applications using the Ruby programming language. Watir integrates with various development tools, making it a good option for regression testing.
- **Sahi Pro** is a regression testing tool for web applications. Testers can use it to automate tests against web applications using the Sahi script language. Sahi Pro integrates with various development tools and supports a wide range of browsers and operating systems, making it a good option for this testing approach.

HeadSpin's data science driven approach toward delivering aggregation and regression testing insights helps professionals monitor, analyze, and determine the changes in the application. HeadSpin offers build-over-build regression and location-to-location comparison with its AI-powered regression intelligence across new app builds, OS releases, feature additions, locations, and more.

_Article resource: This article was originally posted on https://www.headspin.io/blog/regression-testing-a-complete-guide_