What is Regression Testing? The Full Guide

Testlio

November 15th, 2024

Regression testing helps to identify these issues and prevent them from impacting users or damaging a company’s reputation.  

This article provides a comprehensive guide to regression testing, covering everything from the basics to advanced techniques. You’ll learn what regression testing is, why it’s essential, when it should be performed, and how to implement it effectively.

We’ll also share insider tips and best practices that will help you streamline your testing process and deliver high-quality software products.

Table of Contents

• What is Regression Testing? 
• Why is Regression Testing Important? 
• Regression Testing Example
• The Do’s and Don’ts of Regression Tests
• Regression Testing Challenges 
• How to Do Regression Testing
• How to Do Manual Regression Testing
• How to Do Automated Regression Testing
• How to Improve Your Regression Testing Process
• How to Design a Regression Testing Strategy
• In-House Vs. Outsourced Regression Testing
• Final Thoughts

What is Regression Testing? 

Regression testing is when you test parts of the mobile app or software to make sure that new updates haven’t introduced bugs that weren’t there before, ensuring the reliability and stability of software systems after changes have been made.

In other words, regression testing is simply a re-examining of already executed test cases to ensure existing functionality works properly. 

Regression testing covers a wide range of testing techniques, including functional testing, performance testing, and security testing. It also includes testing integrations between different software components and verifying data migration between systems. 

Why is Regression Testing Important? 

Without proper regression testing, every code update becomes a potential risk to the software’s stability and reliability. Even small changes can unintentionally affect core functionality and create hidden bugs. 

Let’s look at five key reasons why regression testing is important. 

1. Maintainability

In agile development, software is delivered incrementally. With the addition of each new increment, it is essential to ensure the system maintains its quality. Regression testing ensures that any impact or ripple effect of new changes is known.

2. Defect reduction

Bug fixes often introduce new issues, particularly when changing the codebase or modifying dependencies. Regression testing helps identify these defects early by focusing on areas prone to instability. 

3. Improved communication 

A common challenge in software development is the lack of communication between developers and testers. Minor changes made by developers may only be noticed if thoroughly tested. 

Regression testing forces a thorough testing of all aspects of the software, ensuring no detail is overlooked.

4. Robustness and stability

Robustness is achieved by thoroughly testing dependent variables and reducing unnecessary dependencies within the system. Regression testing enhances system stability by ensuring each component operates independently without disrupting others. 

5. Cost and time efficiency

Skipping regression testing may save time initially but can lead to costly post-release fixes.

By catching bugs in the regression phase, companies can save on the costs associated with fixing defects in production and avoid damaging user trust. 

Regression Testing Example

One easy example of regression testing would be in a bank’s financial software system, which handles transactions, account management, and customer data. Imagine it undergoes a major update to improve security features and add new functionality for handling loans. 

Once everything has been updated, various regression tests, such as re-testing all transaction types, verifying account creation and closure functionality, security checks, and end-to-end test simulations, among others. 

Let’s go into more detail below.

Pre-Update Scenario:

• Transactions Module: Handles all types of transactions like deposits, withdrawals, and transfers.
• Account Management Module: Manages customer account creation, updates, and closure.
• Customer Data Module: Manages clients’ personal and financial data.

Update Details:

• New security protocols to protect transaction data.
• Addition of a loan management feature within the Account Management Module.

Regression Testing Steps:

• Re-test All Transaction Types: Ensure that deposits, withdrawals, and transfers are processed correctly without any errors and check if the new security measures affect processing speed or accuracy.
• Account Creation and Closure: Verify that account creation and closure processes work as intended with the new updates, ensuring no data loss or corruption.
• Loan Management Functionality: Test the new loan management features to ensure they integrate seamlessly with the existing account management functionalities without affecting the performance or data integrity of other modules.
• Security Checks: Specifically test the new security enhancements across all modules to ensure data protection measures are effective and do not inadvertently block legitimate transactions or operations.
• Data Integrity in Customer Data Module: Confirm that changes in one module (like adding a loan to an account) correctly update the customer’s financial profile without errors.
• End-to-End Testing: Conduct comprehensive tests that simulate real-life scenarios in which a customer might interact sequentially with multiple modules, such as opening an account, depositing funds, applying for a loan, and then making a transfer.

Regression Testing Types 

Regression testing can be conducted in several ways, which are:

• Unit Regression Testing: Involves testing individual code units to ensure changes haven’t introduced new bugs.
• Partial Regression Testing: A portion of the system is tested after minor changes.
• Complete Regression Testing: Testing the entire system after implementing changes; a more thorough approach and typically used after introducing significant changes.
• Selective Regression Testing: A hybrid approach that involves selecting a subset of tests from the entire test suite to be run after updates have been made. These tests are chosen based on their relevance to the changes, and the goal is to ensure that any impacted areas of the system are thoroughly tested.

The Do’s and Don’ts of Regression Tests

Performing thorough and risk-focused regression testing is the key to overall software quality. Understanding the do’s and don’ts of regression tests makes test cycles manageable and efficient.

Let’s take a look at some do and don’ts of regression testing: 

Do: Start early

Implement testing strategies from the beginning of the project to allow for timely bug detection. 

This can be achieved in the following ways: 

• Continuous integration (CI): Implement a CI pipeline with automated regression tests. This enables you to get immediate feedback when the test cases are run automatically with each code commit.  

• Test-driven development (TDD): This practice refers to the process of writing tests before the actual code. It ensures that each new piece of code is instantly validated.

Don’t: Undervalue CI

Agile development and continuous integration pipelines are the most common incremental software development approaches. They allow for requirements and early release flexibility. 

However, these methodologies can only succeed with the integration of regression testing. 

Regression tests enable continuous feedback and improvement, which are necessary for the success of each sprint. That’s why you should ensure continuous integration of regression testing in your development process. 

Do: Automate when possible

Automate repetitive tests that don’t change often. Automated regression tests can run many cycles without worrying about tester availability. This saves time, ensures consistency, and reduces human error. 

Don’t: Rely too much on automation

While automation is the key to continuous testing, some tests like user interface updates need human intervention. Automation cannot evaluate design elements or handle complex and frequently changing apps effectively.

Do: Prioritize test cases

Focus on the critical business features that are most prone to change. For example, in a banking app, prioritize transaction-related tests when adding new security features rather than focusing on less critical areas like adding beneficiaries.

Don’t: Ignore non-critical areas

Even simple code changes can introduce bugs. For example, an overlooked SQL query might affect data display. These minor bugs in small areas can harm the app’s functionality and user experience.

Do: Maintain a comprehensive test suite

Maintenance of the test suite involves updating the test cases promptly and regularly to align with code changes. If test cases are not maintained, it can be difficult to determine how the application behaves with changes and ensure comprehensive coverage. 

Don’t: Neglect test maintenance

Proper maintenance of regression test suites prevents wasting time on obsolete test cases from previous sprints. Review test suites regularly to remove unnecessary tests and avoid false positives or negatives.

Do: Use parallel testing

Run tests in parallel across environments to optimize resources and speed up testing, bug fixing, and development.

Don’t: Skip testing after minor changes

Even small changes can have unforeseen impacts on the system. Therefore, skipping regression tests should not be an option in your testing plan or strategy. 

Regression Testing Challenges 

Regression testing can be tricky and challenging, depending on the software architecture and the nature of code changes. It requires careful planning and strategic solutions to perform impact-focused regression testing. 

QA teams perform detailed risk assessments before executing the regression test suite. This helps pinpoint all impacted areas in the system. 

Let’s take a look at some of the most common regression testing challenges: 

1. Time and resource intensive: Executing comprehensive tests for every update is time-consuming. Each change requires re-testing of all affected modules. 

   This increases the workload and often requires more testers or automation tools. Repetitive testing can lead to fatigue, causing testers to miss critical issues.

2. Automation challenges: Automation tools speed up testing and require technical knowledge and regular maintenance. Over-reliance on test automation can result in missed edge cases or false positives and reduce testing accuracy.
3. Complexity management: As features evolve, the number of test cases also grows. Managing these tests becomes difficult when new functionality is integrated with existing code. To tackle complexity, QA teams prioritize risk-based tests to cover all critical areas.
4. Frequent updates to test cases: Regression tests must be updated regularly to reflect changes. Outdated test cases can lead to gaps in coverage, and test documentation maintenance becomes a challenge for systems with frequent releases.
5. Dependency between features: Changes in one feature can impact others and introduce a ripple effect. Agile teams perform risk assessments before the testing phase to make sure that impacted areas are identified. This helps in executing only relevant test cases. 

How to Do Regression Testing

Regression testing is often performed by re-executing previous test cases on the modified software system to verify that it still functions correctly. Test leads examine the code changes, isolate new features, execute test cases, and create bug reports to tackle issues. 

Here is the step-by-step process on how to perform regression testing:

Step 1: Identify Source Code Changes and Measure Their Impact

The first step in regression testing is to determine the scope and nature of the application modifications. This includes new features, bug fixes, and settings or environmental changes that may affect the application’s performance. 

Through a complete assessment, the application areas that are most likely to be affected can be identified, and the testing efforts can be directed accordingly.

Step 2: Select and Prioritize Test Cases

The next step is to choose the tests for your regression suite. Since you can’t test everything, prioritizing the test cases is also important. 

Use the following instructions to establish your regression testing suite:

• Is the function essential to your product? Is it necessary for other features to function? Core functions must always be checked.
• Is the feature new, and has it been tested against several previous feature updates? New code is often more susceptible.
• Is the code responsive to the environment being configured? Those who are dependent on their environment are more vulnerable.
• Has the code ever been defective? It’s crucial to pay close attention to code that has previously been incorrect.

Step 3: Create a Regression Testing Strategy

The next step is to create a regression testing strategy after understanding the modifications and reviewing the priority test cases. 

As part of this strategy, you should specify the testing goals, scope, timing, resources, and techniques. To develop a realistic strategy, you must be able to estimate the needed time.

Step 4: Set Your Test Frequency

Once you’ve created your regression testing suite, you must specify how often you want the tests to run. 

A regression test should be run whenever a change is made to the code. If your software system is big enough, this can only be accomplished via automation.

Step 5: Use Test Automation

Automation is a key component of regression testing, particularly for agile development teams, where continuous testing is critical. By automating regression testing, hundreds of test cases can be tested faster and more accurately than by a human tester.

Automated tests may be performed rapidly and often, giving real-time feedback on the effects of changes. The time savings from automation grow over time since the same test cases can be reused and replayed with no extra time or effort.

Step 6: Run Manual and Automated Regression Tests

Run the regression tests according to the priorities, beginning with automated tests for efficiency. Manual testing may still be required for complex situations or regions that are not covered by automation.

Step 7: Review Test Results and Resolve Issues

After running regression tests, review the results to discover any failures or problems. Investigate these failures to find the reason, which might be created by the modifications or other factors. 

Fix the problems that have been detected, and then rerun the tests to ensure that they have been resolved. This cycle continues until the application reaches the desired quality level.

Step 8: Revise and Improve the Test Suite

Regression tests must be modified frequently due to the dynamic nature of software development. As new features and modifications are introduced, the test suite should adapt to reflect these changes. 

This involves creating new test cases, eliminating old ones, and modifying existing tests to reflect the application’s current state.

How to Do Manual Regression Testing

Manual regression testing involves real humans executing test cases on a software system after updates, new features, or new ships. 

One of the main benefits of manual regression testing is that it allows testers to identify subtle issues that may be difficult to detect using automated tools.

However, manual regression testing can be time-consuming and expensive, particularly for large and complex software systems. To perform Manual Regression Testing, you have to:

• Determine your regression testing strategy for this round
• List out what updates have been made to the product
• Consider what additional features those updates could have impacted
• Decide what known problem areas or additional testing components will be included
• Divide and conquer the testing surface area
• Create bug reports with steps, screenshots, and videos for easy reproducing.
• Confirm testing coverage with testing resources
• Save and reuse your test cases

How to Do Automated Regression Testing

Automated regression tests involve rerunning previous test cases after software updates are made. However, it depends on the quality of the test cases and the efficiency of the testing tools. To automate regression tests, you have to:

• Identify parts of your application that need regression testing and assess changes each release introduces.
• Select an automation tool that matches your application’s needs and integrates well with other systems.
• Create automation scripts by breaking down test cases into smaller, manageable scenarios.
• Build a comprehensive regression test suite that covers all critical functionalities and areas vulnerable to issues.
• Integrate the tests into your CI/CD pipeline to automate the process and monitor results to address any failures or errors.

Automated Regression Testing Tools

There are various automated regression testing tools available that can help streamline the testing process and ensure accuracy. Let’s explore some of the most popular tools on the market.

Selenium – Selenium allows testers to simulate user interactions, execute test scripts across multiple browsers and platforms, and provide robust reporting capabilities.

Ranorex – Ranorex facilitates regression tests by providing a user-friendly interface and an extensive set of features. With its ability to record, replay, and automate tests across various platforms and technologies, Ranorex streamlines the regression testing process.

WATIR – Watir stands out as a regression testing tool due to its ease in creating, managing, and running test cases. It boasts a user-friendly interface and is particularly suitable for beginners, thanks to its simplicity and cost-effective nature as an open-source solution.

Appium – Appium supports automation across multiple platforms, offers compatibility with popular programming languages such as Ruby, Python, Java, JavaScript, PHP, C#, and RobotFramework, ensuring flexibility in test runners and frameworks. 

Embracing the philosophy of providing a stable WebDriver-based interface, Appium stands apart from other automation tools, ensuring that tests remain uncomplicated even with upgrades.

Testlio – Well, we have to include ourselves in the best automated regression testing tools… that’s just good marketing. Testlio offers both manual and automated regression testing. Testlio’s automated test development enables teams to build and maintain robust test suites using various frameworks and tools. 

By leveraging Testlio’s expertise and collaboration, businesses can efficiently automate their testing processes, including regression testing, to ensure software quality and accelerate release cycles. 

Testlio’s platform offers integrations, advanced reporting, and continuous feedback loops to optimize test coverage and deliver reliable automated regression testing.

These tools allow testers to automate the execution of test cases and identify issues quickly, saving time and effort. 

Automated regression testing tools offer increased efficiency, consistency, and accuracy, but they can be costly, with high initial investment and the need for ongoing maintenance.

The good news is you don’t need to invest in these tools yourself. By leveraging a software testing partner, you can benefit from their stack’s range of automated testing tools to provide fast and reliable testing services.

How to Improve Your Regression Testing Process

There are often problems in carrying out the testing process effectively and successfully.  

To solve this issue, we’ve created a list of best practices for regression tests. These can help software testing teams develop an efficient regression software testing plan and ensure the quality of their software applications.

• Establish a Regression Testing Strategy: A clearly defined testing strategy should cover the frequency of testing and identify the most critical test cases. This strategy should be regularly updated in accordance with the software application’s risk assessment.
• Use Different Testing Methods: A regression test suite should include tests from unit, manual, and functional testing methodologies.
• Conduct Regular Regression Tests: The regression test suite should be executed regularly, ideally consecutive to each new change or release. A proactive approach will ensure early detection and prompt resolution of emerging issues.
• Establish Prioritization for Regression Test Cases: Determine the order of importance and influence on the application for the test cases. This will facilitate the testing of the most critical functions at all times.
• Implement Automated Regression Tests: Automated Regression Testing can greatly reduce the time and effort needed for testing. Additionally, automated tools can help expand test coverage while improving test precision.
• Maintain an Up-to-date Regression Test Suite: It is critical to consistently update the regression test suite to incorporate any modifications made to the software application. This will prevent missed issues during the assessment.
• Collaborate With Software Developers: Collaborate with software developers to synchronize regression tests with ongoing development. This will make any newly implemented modifications easier to test.
• Document the Regression Testing Procedure: Record the testing procedure, including the frequency of testing and the test cases. As a result, the testing procedure will be able to be replicated and be consistent. Maintain a record of any software defects discovered during testing and disclose them to the customer.
• Improve the Software Regression Testing Method: Constantly improve the process of regression testing by examining outcomes and implementing necessary modifications. As a result, testing procedures will be consistently effective and efficient.

How to Design a Regression Testing Strategy

A solid regression test strategy includes four main components: specific testing objectives, the scope of testing processes, entry/exit criteria, and test suite design. 

These components are established early in the application development lifecycle to optimize quality assurance. 

Here’s a breakdown of the four components necessary for designing a regression testing strategy:

Testing Objectives 

This phase involves identifying potential risks associated with the application, which inform the scope of regression testing. Questions to consider include the impact of potential failures on end users and the organization, as well as what level of risk is acceptable.

Scope 

Determined by the identified risks, this includes considering both functional and non-functional aspects, and defining which test types or methodologies are included or excluded.

Entry and Exit Criteria

These criteria set reasonable parameters for beginning and concluding regression tests. An example of entry criteria might be the requirement of a certain number of successful test sprints, while exit criteria are aligned with the team’s definition of “done”.

Test Suite Design 

The focus is on designing the test suite to achieve maximum coverage with a minimum number of test cases. 

Key considerations include which applications and services are tested, the frequency of tests, the necessary environments for development and testing, and strategies for addressing high-severity bugs.

Regression testing is improved through thorough preparation and a clear framework for effective regression testing.

Regression Test Cases 

Amazon, the world’s largest e-commerce platform, relies heavily on its website for sales, making regression testing necessary for maintaining its functionality, reliability, and performance. 

For instance, introducing a new product category, such as “Smart Home Devices,” involves several regression tests:

• Homepage Functionality: Check that the homepage accurately lists the new “Smart Home Devices” category without disrupting the layout or functionality of existing categories.
• Category Navigation: Confirm smooth navigation to and from the new category page.
• Search Functionality: Test that the search feature correctly filters and displays results for smart home devices, keeping them distinct from other categories.
• User Accounts: Ensure that user accounts function properly for creating, updating, and making purchases in the new category.
• Payment Processing: Assess payment systems to ensure they handle transactions for the new category securely and without errors.
• Mobile Responsiveness: Verify the site’s responsiveness on various devices, particularly when accessing the new category.

If these tests uncover any functional regressions, they must be documented and addressed promptly to prevent impacting the user experience. Continual testing, especially after updates or expansions, is crucial, and automation can significantly streamline this process.

In-House Vs. Outsourced Regression Testing

When it comes to any type of testing, you have two options: in-house or outsourced testing. In-house testing requires an internal team, which can be expensive and time-consuming. 

However, it provides the advantage of having complete control over the testing process and the ability to integrate testing into the software development life cycle.

Outsourced testing involves hiring a third-party provider to handle the testing process. This can be cost-effective and convenient, as the right provider can offer an expert team and the latest testing tools, but choosing the right partner is essential.

Ultimately, deciding which to use depends on budget, timeline, and internal expertise. At Testlio, we offer the best of both worlds—you can choose from both in-house and outsourced regression testing services to build your ideal scenario.

Final Thoughts

Correctly using regression testing methods and tools can identify and eliminate all surfaced defects early in the development process. 

At Testlio, we’ll work with you to develop comprehensive test cases that are tailored to your specific needs. By ensuring a robust set of test cases, you can be confident that your product will continue to perform well after updates.