What is Regression Testing? | Comprehensive Guide

If you’re new to software testing, you may not know what regression testing is. A simple explanation of regression testing is that it is the process of testing software without affecting how the software works. 

After reading through this guide, you will know everything about regression testing, including how it works, the different types of testing and techniques, challenges, and best practices for implementing test automation in regression testing. 

Regression Testing 101

Regression testing is the process of testing new software. This is done to ensure that it works as it should and there are no bugs, known as regressions, hence the name regression testing. 

Software development requires continuous functional testing, and regression testing includes running many tests. Reusing old functional tests is an important part of regression testing because new or updated software can sometimes develop old problems and defects that it previously had. 

Software engineers will use regression testing when they have updated or modified the software, fixed previous defects, or made other changes to the code. The smallest changes can have big side effects. A case that highlights the importance of regression testing is Microsoft’s 2020 software flaw shock. According to major news outlets, the National Security Agency discovered a software flaw in Microsoft’s Windows Operating system that left users vulnerable to hacks. This is an example of something that could have been discovered and remedied by means of regression testing.  

Regression testing is so important and useful throughout the development process because it does not limit or affect the core functionality of the software and user experience. This results in a very small impact on business operations. 

Types of Regression Testing

There are at least seven different types of regression testing, and they have different levels of importance and complexity. For example, larger projects may require complete ongoing testing, while others may require less intensive tests like the particle or unit regression tests. 

Let’s have a look at the three most important types of regression testing. 

Unit Regression Testing 

This type of testing is done during the unit testing phase and is very important, as it can detect bugs or potential problems with code early in the development process. The unit testing phase is the process of testing and verifying software code and is one of the oldest tests in software development. 

Unit testing involves every line of code in the software to check that it works. The developer writes unit tests, which test the smallest unit of the software, which can either be comprised of code or a test method. 

During this process, only individual code is isolated and tested. This can be done either manually or automatically with a software testing tool. Individual testing of units helps to prevent any discrepancies or effects from other bugs in the software. 

Partial Regression Testing

Partial regression testing is a type of test that is typically used to verify new code that has replaced existing code. This is done after the new code has been added and tests that the entire system still functions as intended. 

This type of testing is used if only one block of code was added or changed or if slight changes were made to the software. During this testing process, developers will test the new code by making it interact with the old code. 

Complete Regression Testing

This is the most comprehensive type of testing, and it is used when multiple new blocks of code, functions, and changes have been added to the software. Complete regression testing, also known as the final regression test, is used when developers are unsure of how new or updated code will interact with the current functionality of the software. 

Complete regression testing will test the software as a whole rather than isolated code or modifications. This complete regression test is used as the final test before the software is released, and it allows developers to feel confident in the capabilities of their software. 

Regression Testing Techniques

To ensure that all potential bugs and defects have been resolved, different regression testing techniques are used. These are the retest-all approach, the test selection techniques, and test case prioritization. 

Retest-All Approach

This type of testing technique is one of the largest in scope because it takes a lot of time and is extremely costly, but it is also the most comprehensive, testing the entire program. 

This type of complete testing is unnecessary for smaller programs with minor changes. However, larger projects with harder-to-predict regressions, multiple changes, new requirements, and new code will require this approach. 

The retest-all approach can be used on software that has had new language or other features added, like number formats, dialog boxes, currency, time and dates, as well as supporting new character sets.

Test Selection Techniques

Instead of running a complete test, the test selection technique uses a set of test cases from regression test suites. Regression suites are where all the tests are stored to test the outcome of a specific code or change that was made to the software.

There are two parts to the test selection technique. The first part focuses on identifying the affected code. The second part involves determining the most appropriate tests to be used. 

There are two types of tests from the test suite that can be used. These are reusable test cases and obsolete test cases. 

Reusable test cases are tests that can be used multiple times as well as during future regression tests. Obsolete test cases cannot be used in future regression tests. 

Test Case Prioritization

This type of testing technique is where the tests are prioritized depending on a number of different factors, including:

• Critical functions of the software 
• The impact on the business 
• The security risks associated with the software, such as protecting credit card information

These factors will influence what tests will be used and in what order higher priority tests will be favored over lower. Regression testing can be time-consuming and very costly, so developers need to be smart about what they use from the test suite. 

Regression Testing Challenges and Best Practices

There are a number of challenges that developers will run into during regression tests, but the two most common problems are time and money constraints. The larger the project, the more tests are needed, and this can be very time-consuming.  

It can be difficult to achieve maximum test coverage with limited resources for large projects. Automated tools can help improve the efficiency of these tests and software applications. However, they come with huge costs that many small businesses cannot afford. In this case, developers will use test selection techniques and partial regression tests if no big changes are made.

To combat some of these challenges, developers have come up with a set of best practices to ensure they get the best possible results in a more timely and cost-effective manner.  

Best practices for successful regression testing include: 

• Performing regular tests after changes to avoid having to fix all major defects at the end of the testing phase and run expensive complete regression tests
• Providing checks to ensure all regression tests are up-to-date
• Rerunning successful regression suite test cases
• Automating regression testing with regression testing tools where needed

Implement Test Automation in Regression Testing

Manual testing can be extremely time-consuming and costly, as well as difficult to ensure full coverage if working on large projects. Making use of automation tools like Ranorex in the regression testing process can drastically speed up the process. 

Automated testing is preferred when looking to reduce the number of mistakes made by human error, increase test coverage, and result in a faster turnaround time. Tests can be set up to run 24/7 to ensure early detection of any bugs or potential problems. 

Regression testing can be expensive, especially if multiple people are hired to run tests and monitor the process. While setting up automation tools can be costly, in the long run, they can reduce costs by removing the need for human supervision or a large testing team. Automated testing can be designed to automatically prioritize and run the relevant tests after each new update or modification. 

For your automated regression tests to be successful, though, it is important to create a relevant and comprehensive test case script that you want the automated software to follow. Add frequent checkpoints throughout the testing process. 

There are plenty of different automated tools available, so it’s a matter of choosing one that suits your specific needs and budget.   

Leverage Ranorex for Regression Testing 

Improve the efficiency of your regression testing by using reliable automated software like Ranorex’s flagship product Ranorex Studio. Ranorex’s software test automation tool is trusted by more than 4,000 software QA teams and software developers to automate testing so that teams can release faster while reducing defects and saving money on testing.

Included in the Ranorex software are the Selenium WebDriver and Selenium Grid to provide efficient, fast, and codeless testing. You can learn more about Ranorex here.