Non Regression Testing: Purpose, Process, Examples

Testlio

November 22nd, 2024

The rapid growth of the market proves the importance of reliable testing practices, including non regression testing. 

A major challenge in software development is making sure new code changes do not introduce bugs or disrupt existing functionalities. 

Non regression testing addresses this by re-running tests to ensure recent updates have not affected existing functionality. It acts as a safeguard, maintaining the integrity of the application.

In this article, we will discuss the growth of the software testing market, challenges from code changes, the role of non regression testing, its benefits, and best practices. 

What is Non Regression Testing

Non regression testing is a software testing technique that aims at verifying that new or modified functionality works correctly without affecting previous functionality.

Non regression focuses on the developing unit or module instead of the full product, saving you time and resources. It improves resource efficiency by focusing on modified parts rather than retesting the entire application.

The stable code represents the base code that has been thoroughly tested and is functioning properly. 

The second step involves new feature development. During this phase, the codebase is being actively worked on. 

Non regression tests are performed to ensure that the newly developed features do not negatively affect the current system. 

The code remains stable as changes are added, but new features are being integrated and tested separately.

Finally, the entire codebase is stable, meaning that it has passed the tests and no issues are present from either previous versions or new changes.

Additionally, it mitigates risks by identifying potential issues early in the development cycle, reducing the likelihood of major defects in production. 

Types of Non Regression Testing

Here are types of non regression tests:

1. Corrective Non Regression Test: Uses existing tests to verify that no new bugs have been introduced, provided no major changes have been made to the product.
2. Full Non Regression Test: Involves re-testing all elements of the product to verify all changes made since the beginning.
3. Selective Non Regression Testing: Selects certain tests from a set to inspect only those parts of the code that have been impacted.
4. Progressive Non Regression Testing: Creates new tests when established tests are no longer useful, especially when product characteristics change.
5. Partial Non Regression Test: Performed when different modules are under development and about to be merged with the main version of the code.
6. Unit Non Regression Test: Tests individual units of code without considering other elements.

Difference Between Regression and Non Regression Testing

Regression testing and non regression testing play different roles in maintaining the quality of software.  A regression test verifies that recent code changes have not broken existing functionality. 

Non regression testing targets specific areas of the software to verify that updates or new features do not introduce new bugs. 

Here is a detailed comparison table for each type:

Objectives of Non Regression Tests

The main objective of non regression testing is to ensure that new features to software do not negatively impact existing functionality. 

Here are the other key objectives of non regression testing:

• Verify New Functionality: Ensure that newly added features or modifications work as intended without introducing new bugs.
• Maintain Stability: Confirm that the software remains stable and reliable after changes, preventing any disruption to existing functionalities.
• Detect Side Effects: Identify any unintended side effects caused by recent updates, ensuring that they do not affect other parts of the application.
• Improve Quality: Enhance the overall quality of the software by ensuring that both new and existing features function correctly together.
• Resource Efficiency: Save time and resources by focusing testing efforts on the modified parts of the software rather than retesting the entire application.

When to Perform Non Regression Testing

Non regression testing is performed at various stages of the software development lifecycle. The following times are ideal for non regression testing:

After Bug Fixes

When bugs are fixed, it’s important to verify that the fixes do not introduce new issues or affect other parts of the application.

Post-Feature Addition

Whenever new features are added, non regression testing ensures that these additions do not disrupt existing functionalities.

Following Code Refactoring

Refactoring code can improve performance and maintainability, but it can also introduce new bugs. Non regression testing helps ensure that the refactored code works as intended.

During Integration

When integrating different modules or components, non regression testing ensures that they work together without causing regressions.

Before Major Releases

Conducting non regression testing before major releases helps catch any issues that might have been introduced during the development cycle.

After Environment Changes

Changes in the environment, such as updates to the operating system, database, or other dependencies, can affect the software. 

Steps of Non Regression Tests

Non regression testing involves a specific set of steps. The following steps are key to non regression testing:

1. Establish a Benchmark Software Release: Identify a stable version of the software that will serve as a benchmark.
2. Define Test Routines: Create a set of test routines that can simulate as many software functions as possible. These routines should cover both the new and existing functionalities.
3. Execute Test Routines: Run the defined test routines on both the benchmark release and the new release under test. It’s important to maintain the same test environment for both versions, which helps in comparing their behavior.
4. Collect and Analyze Data: Gather data from the test executions and use post-processing tools to analyze the results. This analysis helps in identifying any errors or regressions.
5. Report Outcomes: Document the findings from the analysis, highlighting any issues or regressions detected. This report should be shared with the development team for further action.
6. Iterate as Needed: Based on the findings, make necessary adjustments and re-run the tests to ensure that all issues are resolved and no new regressions are introduced.

Challenges in Non Regression Testing

Non regression testing, although crucial for maintaining software quality, presents several challenges that can complicate the testing process. 

Teams need to understand these challenges to implement non regression strategies and make sure their software is reliable. Here are some of the challenges:

1. Incomplete Test Coverage

One of the primary challenges in non regression testing is achieving comprehensive test coverage. 

Testers may neglect or overlook certain functionalities or scenarios, particularly if they focus only on new or modified features. 

This can lead to critical bugs remaining undetected, which may affect user experience or system performance. 

The best way to mitigate this problem is to maintain a well-organized test suite that includes all relevant test cases and scenarios. 

Test management tools can help track coverage and ensure all functionalities have been adequately tested.

2. Resource Constraints

Non regression testing can be resource-intensive, especially in complex applications where multiple features may be interdependent. 

Limited time and personnel can restrict the ability to perform thorough testing, leading teams to prioritize certain areas while neglecting others.

To address resource constraints, teams can adopt automated testing tools to automate repetitive tasks and increase efficiency. 

3. Rapid Development Cycles

Agile development environments often use CI/CD practices, but the speed of development can slow down non regression testing. 

It can be challenging to manage code changes effectively when they occur frequently.

This risk can be mitigated by implementing a CI/CD pipeline that includes automated non regression tests. 

With automated tests, teams can ensure that new features do not disrupt existing functionality without slowing down development.

4. Ambiguous Requirements

Ambiguity in project requirements can lead to discrepancies in how non regression tests are executed. 

Testing outcomes may differ depending on how what needs to be tested is interpreted. 

This may cause missing functionalities and inconsistent testing outcomes. This challenge can be overcome through clear communication and documentation of requirements.

5. Dependency Management

Software applications often have several dependencies on external libraries or services.

If these dependencies change, false positives and negatives may result during non regression testing.

The teams should be able to maintain a current inventory of all external components and their versions to manage dependencies effectively.

As part of the non regression strategy, these dependencies are regularly reviewed and tested to identify potential issues.

Best Practices for Non Regression Testing

To make non regression testing effective, teams can adopt these key best practices:

Establish Clear Objectives

A clear set of goals should be defined before implementing non regression testing. 

This includes specifying which functionalities need testing and the expected outcomes. Clear objectives help focus efforts on critical areas.

Maintain a Comprehensive Test Suite

A comprehensive test suite should cover all existing functionalities. This suite should be updated regularly to reflect any changes in the application. 

A well-maintained test suite assures that all relevant scenarios are tested, reducing the risk of overlooking important functionalities.

Automate Where Possible

Automated testing tools can simplify the non regression testing process by executing tests quickly and repeatedly. 

Automation improves efficiency and reduces the need for manual intervention. 

Tools like Selenium and CI/CD integration platforms can support these automated tests as part of the development process.

Integrate with CI/CD Pipelines

Non regression testing should be incorporated into continuous integration/continuous deployment (CI/CD) pipelines. 

This integration allows automated tests to run whenever code changes occur. Continuous validation maintains software quality throughout development.

Prioritize Test Cases

Testing efforts should prioritize high-risk areas and critical functionalities. 

By focusing on these areas, teams can optimize resources and improve stability, particularly for functionalities that impact user experience.

Conduct Exploratory Testing

Alongside scripted tests, exploratory testing can be part of a non regression strategy.

Exploratory testing allows testers to interact dynamically with the application, identifying issues that may not appear in standard test cases. 

This approach uses human insight to uncover potential regressions effectively.

Regularly Review and Update Tests

Test cases should be reviewed and updated regularly to reflect changes in functionality, user requirements, or technology. 

This ensures that tests remain relevant and effective in identifying regressions, especially as new features are added or existing ones modified.

Document Test Results Thoroughly

Detailed documentation of test results, including any identified issues and their resolutions, should be maintained. 

Comprehensive documentation helps in tracking regressions over time and provides valuable insights for future testing cycles.

Examples of Non Regression Testing

Non regression testing can be applied in various scenarios to ensure that changes to teh product or app do not negatively impact existing functionality. 

Here are some examples:

Automated Testing

Automated test suites are invaluable for non regression testing.

For instance, a web application might use Selenium to automate browser interactions and verify that recent changes do not break existing features.

Unit Testing

Developers write unit tests to validate individual components of their code. 

For example, if a new function is added to a library, unit tests can ensure that this new function works correctly without affecting other functions.

Integration Testing

Integration tests verify that different parts of the software work correctly together. 

For example, after integrating a new payment gateway into an e-commerce platform, integration tests can ensure that the new gateway works seamlessly with the existing order processing system.

Functional Testing

Functional tests validate the software’s functionality from a user’s perspective. 

For example, after adding a new feature to a mobile app, functional tests can ensure that the new feature works as expected and does not interfere with existing features.

Backward Compatibility Testing

When updates or changes are made, it’s crucial to check if the software remains compatible with previous versions and configurations. 

For instance, after updating a software library, backward compatibility tests can ensure that applications using the older version of the library still function correctly.

Exploratory Testing 

Testers often use exploratory testing to uncover unexpected issues or scenarios that automated tests may miss. 

For example, after a major UI overhaul, exploratory testing can help identify usability issues that were not anticipated during automated testing.

Automating Non Regression Tests

Automation maintains existing functionalities while allowing the addition of new features. Here are some best practices for automating non regression testing:

Choose the Right Tools

The choice of automation tools significantly impacts testing success. 

Tools like Selenium, Statsig, and testRigor offer reliable frameworks for automating tests and integrate smoothly into CI/CD pipelines.

Integrate with CI/CD Pipelines

Automating non regression tests within CI/CD pipelines enables tests to run automatically with every new code commit. 

This integration catches regressions early and ensures continuous feedback throughout development.

Prioritize Test Cases for Automation

Not all tests benefit equally from automation. Therefore, prioritize repetitive tests and tests for high-risk areas critical to functionality. 

Automating these cases saves time and reduces manual error.

Maintain a Dynamic Test Suite

Regularly update the automated test suite as features evolve. 

Keeping test cases relevant prevents outdated tests, reducing the risk of false results and maintaining accuracy in regression testing.

Use Hybrid Approaches

A hybrid approach combining automated and manual testing provides comprehensive coverage. 

Automation handles repetitive tasks, while manual testing addresses complex scenarios that require human insight.

Implement Real-Time Monitoring and Reporting

Real-time analytics and reporting streamline issue detection. 

Tools like Statsig offer immediate insights on test performance, helping teams prioritize and resolve issues faster.

Focus on Test Design

Effective test design is necessary for automation. 

Clear, maintainable test scripts aligned with business needs make tests easier to update as the application evolves.

Train Team Members

Proper training means the team not only understands your product well (tribal knowledge) but also can effectively use automation tools and understand best practices, which improves the quality and consistency of automated tests.

Monitor Automation ROI

Assessing the return on investment (ROI) from automation reveals its value. 

Metrics like reduced testing time, increased coverage, and fewer defects indicate the effectiveness of automated non regression testing.

Final Thoughts

Non regression testing plays a critical role in making sure that software updates and modifications do not introduce new issues or compromise existing functionalities. 

By focusing on specific areas impacted by code changes, non regression testing allows teams to catch potential bugs early. It helps maintain application stability, and efficiently allocate resources. 

For teams looking to improve their non regression testing approach, Testlio offers comprehensive solutions that simplify testing workflows and enhance software quality. 

Explore Testlio’s testing services or contact our team to learn how we can support your quality assurance needs and drive better outcomes for your projects.