What is regression testing ? - explained with an example

For example :

  • In an online banking application, under the bill payments section there is a new feature of "adding a payee" that needs to be implemented to enhance the product quality.

  • The testing teams need to create test cases to test this newly added functionality in the application.

  • The testing team will perform the execution of all these existing modules in the regression cycle.

  • Also once the “Add Payee” feature is stable, for any feature the “Add Payee” feature test cases will also be added to the regression test suite.


Importance of regression testing in software development

  • Regression testing is the major and important part of any software development as it checks the complete functionality after the newly added feature has been verified to be stable.

  • Regression testing verifies if the functionality is working as previously after the new changes are made to the software.

  • Agile methodology increases the risk visibility at an early stage of the project development life-cycle. Regression checks the stability of the system after new additions to it. So, the importance of regression testing in agile methodology for software development grows manifold.

  • Regression testing aims at performing continuous testing. Continuous testing helps in the overall quality and stability of the software.

  • As regression testing begins at an early stage it decreases the probability of missing the hidden requirements.

  • Finding and reporting a defect at an early stage of software development prevents excessive rework. This ultimately helps the testing team to meet the release timelines and deliver bug free software.

  • Regression testing is one of major factors in gaining customer confidence by living up to their expectations in terms of delivery and software quality. Organisations can showcase their ability in terms of efficient software delivery by adopting regression testing process in the test cycle.

  • Regression testing helps the team to identify the defects and eliminate them earlier in the software development life cycle. It eventually improves overall user experience for the developed software.

  • Regression testing ensures continuity of business functions with any rapid change in the software. Also since automated test cases saves the execution time, the testing team can focus on covering more areas of the software.

  • With the increasing demands for the quality of product, implementing automation regression testing in agile guarantees faster shipping of the product to the market.


Advantages of Regression Testing

Regression testing is the critical need in the agile competitive market. The software market growth depends on the regression testing success rate. Where functional tests ensure the proper functioning of the software, regression testing needs to be run to ensure applications stability during each sprint at every stage.

The many advantages of regression testing gives the target users an assurance that the new code changes are not affecting the existing features in the software. The Agile DevOps team can't compromise on skipping the regression cycle as the bugs will be encountered by the end users. This becomes a threat to the reputation and credibility of the software industry.

The testing team needs to be well aware about the advantages of regression testing that makes regression testing essential in every test cycle.

  • Regression testing plays a crucial role in an agile environment where with every sprint, the integration of previous and the current release has to be ensured. Regression guarantees continuity of business operations.

  • Regression testing helps to identify the bug in the software by catching the undefined integrations between the modules in an application. With regression tests, the software is made resistant against discrepancies. This provides support to the testing teams to release the product faster with quality assurance.

  • Regression testing ensures even with these constant additions, the application strives to remain intact and integrated. Automated regression tests generate faster results and enable repeated testing for similar releases. This helps to track any kind of error in an application on a constant basis.

  • Automated regression testing substantially increases the testing process and shortens the testing lifecycle. Automation scripts can be run overnight as well across various machines at the same time period. Once the automated regression test suite is ready and can be utilized for execution, the test resources can focus on other needed areas of the application that require their expertise.

  • It helps to gain customer faith and thereby achieve higher CSI(Customer satisfaction Index) and eventually can be considered as a major reason to expand the business.

  • Regression testing ensures a fix does not adversely impact the existing functionality. Along with pushing the new additions to software in the production, the team ensures the existing features remain unaffected.

  • Regression testing helps to reduce unnecessary expenses that call for incidents in production. The cost of the overall project is also minimized by using automated software testing solutions.

  • Regression testing also helps implement a continuous integration setup in which whenever the developer pushes a code, a build is triggered post which the regressions test suite is automatically executed to ensure smooth functioning of the entire software.

  • Automated regression test cases save a lot of time in execution as same automated test scripts can be reused for testing and modified on need basis.

  • It promotes the improvement of the product quality, and it verifies that any modifications that have been done to not impact the core functions already tested and proven.

  • Regression testing can be performed both manually and by automation. Ensure to have a process in place for updating the regression test scripts as per the business objectives. Adopting automation in regression testing can save project cost to a great extent. Automation is ranked as the main advantage of regression testing.

  • Regression testing outweigh the risks of skipping it.

  • Regression testing allows to detect and fix the bugs in the software before being shipped to the market.

Understand these advantages of regression testing and fully regression test your application to avoid issues in production.


When does regression testing occur?

Regression testing is always driven by change - change in terms of the application under test. If there is a change in the code, regression testing at some point of time is essential to avoid a regression.

Regression testing should occur in case of the following scenarios :

  • Regression should be performed on every single build that is deployed to avoid the issues from reaching the user. Another reason is, if a bug is identified soon after it is introduced corresponding to a commit, the developer will have a better chance to fix it. Automating the regression test suite helps us achieve this goal in much less time.

  • Begin the regression cycle during the start of the second round of testing, i.e. when the defect fixes start rolling in. This will help to ensure that existing functionality is not impacted by the scope change / new feature. If your regression test suite is complex and large, you need to prioritize the test cases to be executed.

  • Begin the regression cycle during the start of the second round of testing, i.e. when the defect fixes start rolling in. This will help to ensure that existing functionality is not impacted by the scope, change / new feature.

  • Regression testing happens whenever the DevOps team is expected to deliver a new feature to production. The team ensures along with the additional features the existing ones should also function smoothly.

  • Regression testing (Retest failed test cases) also occurs post retesting of a fixed bug. There's a possibility while fixing bugs and performing some code modifications, other portions of code is also affected. This eventually disturbs the operation of the existing features of the software. Hence, one round of regression testing is needed post defect retesting to ensure smooth functioning of all the features of the software.

  • Regression testing in agile also occurs when the developers rebuilt the existing functionality as per the latest technology for eg. a service which was developed in Tibco technology is now being rebuilt using Java. In such situations, regression testing checks whether the feature or service in question was modified with no damage to the rest of the functionality.

  • Regression testing is performed whenever there's a change request (CR) initiated by the client which requires code changes in the software.

  • Whenever there are performance issues or application crashes concerns reported by the customer, regression testing is much needed here.

  • Regression testing is also to be performed when the UI(User Interface) of the application is changed to make it more user-friendly.

  • Regression testing is performed when there is integration between two or more modules. Here, regression testing ensures the software product works flawlessly after integration with another product.

  • Regression testing occurs when the code is migrated on an advanced technology platform. Whenever there is a critical bug identified in the testing phase and fixed by the developer, post the fix, regression testing is essentially to be performed.

  • After any patching activity it's quite possible the existing functionality is not working on expected lines. Regression testing is important to be carried out after every patching activity.


Application of Regression Testing

Automated regression testing is ideally recommended under the following circumstances :

  • As often as possible for a stable build every single time.

  • Automated regression testing needs to be part of the build process. Ensure the tests are executed on regular intervals based on the build cycle, cost of execution, and result investigation. This set of regression tests needs to be executed and maintained through the entire development cycle.

If your regression test suite is complex and large, you need to prioritize the test cases to be executed. Focus on testing only those areas which are directly impacted by the scope change.


The problem with regression testing

Let’s discuss the problems with regression testing :

  • The major issue with regression testing is the stringent timelines. With every change in the software, the testing team needs to ensure the existing functionality is not adversely affected in any sense. The regression test cases have to be executed repeatedly within the reduced regression cycles in sprint.

  • Optimizing the test cases in regression testing sometimes is difficult. As the scale of regression testing grows with every sprint, more number of automation test cases are difficult to maintain. It becomes necessary to accommodate these changes in the regression test cases.

  • Even with automation, regression testing involves running existing test cases multiple times. It takes a lot of time to complete the regression cycle. With every new additional feature, the number of times the amount of regression testing to be done only increases.

  • It might be difficult for someone new in the team to intervene halfway to understand what is being changed and what is being affected.

  • To perform smooth regression testing, the environment in which the testing is to be done has to be stable. Environmental issues while regression test execution can simply delay the execution process. If this happens on a regular interval we might also compromise on the concentration of testers to identify and report bugs.

  • Lack of communication between cross functional teams during regression testing also leads to problems.

  • Identifying the test cases in every module a change is made takes time, it is very likely that we miss to consider the test case which is critical to validate this change. It's very time consuming to figure out the test cases to be executed in the regression cycle. It is quite possible while choosing and selecting the test cases for execution, we might miss to check the critical functionality.

  • To perform smooth regression testing, the environment in which the testing is to be done has to be stable. Environmental issues while regression test execution can simply delay the execution process. If this happens on a regular interval we might also compromise on the concentration of testers to identify and report bugs.

  • Testing in the midst of code changes is not easy to implement and maintain.

  • The selection of the right automated tool also matters before we begin regression testing. Record and playback tools often don't work well in automated regression testing since it involves a lot of rework.

  • Regression tests need to be scripted and run on an automatic build environment. Automated regression tests need to be integrated within each sprint to work on the feedback continuously to address the defects as and when they are introduced to avoid late hardening sprints.

  • Regression tests need to be run after every development iteration and also after changes are made. There could be a lot of application stability or deployment issues observed during regression. This can slow down the overall testing.


Benefits of Regression testing

Listed below are the benefits of regression testing :

  • Regression testing in agile promotes and maintains the software quality of a product. It helps in boosting the testing teams confidence in delivering a high end bug free software to the customer.

  • Regression testing in agile ensures the issues already detected are fixed now and we are ready to deliver an efficient software into production.

  • Regression testing ensures the modification to enhance the software does not have any side effect on the existing deployed code.

  • Automated regression testing in agile is the key aspect of software testing as it mainly increases the test coverage in less time.

  • Regression testing in agile executes specific scenarios to ensure the functionality works smoothly.

  • It lets the organization know which defect is causing issues in the application post software changes and hence prevent from sneaking these incidents into production.

  • Regression testing in agile ensures system stability while enhancing the application in better ways.

  • As regression testing executes the same steps repeatedly and allows the team with shorter sprints to deliver better quality products to the customer.

  • As automated regression testing saves time and manual labour being spent on repetitive tasks it is quite cost effective.

  • Regression testing in agile helps in identifying the problematic areas at an early stage so that the developers can immediately replace that section with proper code, It also helps achieve better software reliability.

  • As the regression test scripts are fully automated, it helps to reduce the overall execution time by saving considerable time and effort.

  • As the tests developed in the regression testing cycle are reusable, for any upcoming sprint cycle the regression test suite of the previous cycle is readily available for the test execution phase. Such a software testing generates high ROI (Return on Investment).

  • Regression testing is the means by which we assure the customer the final product delivered effectively meets his expectations.

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Disadvantages Of Regression Testing

  • Manual regression testing requires a lot of human effort and time and it becomes a complex process. If automation tool is not being used for regression testing then the testing process would be time consuming.

  • Regression testing has to be performed for every small change in the code as even a small portion of code can create issues in the software.

  • Regression testing needs to be done repeatedly each and every time in the agile sprint.

  • For complex functionalities we need to design huge test scripts which take a lot of time to execute. This might delay the test execution process and the testing team might fail to meet the delivery timelines.

  • In regression testing we aim to achieve maximum test coverage with the creation of limited test cases. This becomes difficult when we have stringent timelines

  • It becomes difficult for the testing team to determine the frequency of regression tests after every release and build of bug fixes.

  • It becomes difficult to track the test execution time when there are changes in business requirements that are communicated in between the sprint and are to be delivered on priority So the scrum teams need to be prepared to accept the late change in requirements.

  • Lack of understanding on the business requirements leads to improper creation of regression test suites. If we don't have proper regression test cases in place the testing team might miss on testing and reporting the critical functionality defect.

  • If the testing team does not understand the software development methodology they have adopted, there will be issues in planning the regression testing.

  • If the testing team does not understand the purpose of regression testing they follow wrong steps in the regression test execution process.

  • If the regression testing team does not possess adequate information on the application and the business requirements it will be difficult to perform a good regression testing.

  • If the testing team has done bad impact analysis or has no clarity on the changes in software it will be difficult to achieve good test coverage. This will eventually result in bad regression test execution.

  • It's a big challenge to perform regression testing under the time and resources constraints.


What are the risks in regression testing ?

In order to achieve good automation regression testing results, the testing team needs to be proficient enough to possess good knowledge on the automation test techniques right from selection of tool and creation of automation test scripts to perform the test execution. Lack of automation expertise in the team can lead to a bad automated regression testing.

Let’s try to understand the risks associated in regression testing with an example :

  • Many times there is a customer who needs to rebuild an existing application built on a certain technology to a more advanced technology platform.

  • The developers will implement the functionality using the advanced technology and hand it over to the testing team for testing purposes.

  • There are chances that the testing team does not hold sufficient knowledge on the functionality of an application. In such a scenario there is high risk involved as the regression testing can go haywire due to lack of application insights.

  • The regression risk grows exponentially as the application ages.

  • Even if the recent team did their best to understand the underlying design and structure , it’s very unlikely the changes they incorporated in the application fit with the original design theme.

  • After several years , the software is bound to be enhanced so many times by the team who were not involved in the original development.

  • The size of regression suite increases over time as the system grows in terms of functionality and complexity. Each new release faces the same constraints in terms of budget, schedule and team size. The complexity of the system is increased as more and more code is developed for new features and the interaction of various modules in the system increases.

  • These kinds of changes make the system grow more complex until it becomes brittle.

  • The system level dependencies are difficult to be understood by the team. As the team is uncertain on how to test the application, it ultimately results in insufficient test coverage of the system.

To be able to overcome these risks and challenges in regression testing, the team can come up with a risk based testing plan that helps to assess these challenges.


How to manage risk in regression testing ?

Agile teams are responsible to make incremental delivery which means as the number of iteration increases, the size of the product also increases significantly. Hence the risk of regression is proportional to the product. As the product size increases , the risk of regression as well increases.

The testing team needs to be prepared in advance to have a proper plan in place to mitigate the regression risk. Having extensive automated regression test suites can definitely help mitigate the risk. In every iteration the testing team needs to keep on updating the automation test scripts. The automated test cases can be stored in the configuration management tool so that it becomes easier to retrieve on need basis.

If the test cases history is available to the testing team, it benefits the team in troubleshooting any major problem. The testers at the beginning of the test execution can prepare a test strategy document specifying how the regression testing needs to be carried out. The testing team needs to review the tests written earlier in order to be able to add, update or delete any test script.

Post regression testing team can plan a sprint review with all the stakeholders and give a demo of the developed and tested application and further retrospect on improving the same based on the suggestions received. Certain prerequisites like generating test data, test data loading, build deployments can also be automated to minimize the risks.

Using a risk-based testing strategy will significantly reduce the regression risk that stands inherent in making small changes to a large system.

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Retesting is done after a bug-fix. It is re-execution of all the test cases that were failing because of a bug and should now pass after the bug is fixed. While, regression testing is execution of test cases to test the stable areas that may have been impacted by the fix. Regression Testing is not specific to a bug fix, it can be done after a change is done to the environment. The change could be - a new feature, an enhancement or an environment change but retesting is specific to a bug fix.

Read more to know about the differences here.

Common types of regression testing include :

  • Corrective Regression Testing : This type of testing is used when there are no changes introduced in the product's specification and the existing test cases can be used for performing these tests.

  • Retest-all Regression Testing : This involves testing all aspects of a software as well as reusing all test cases even where the changes have not been made.

  • Selective Regression Testing : In this type of testing, a subset from the existing test cases is used which reduces the effort required for retesting and the cost involved.

  • Progressive Regression Testing : This type of regression testing works best when there are certain changes done in the program specifications as well as new test cases are designed. This ensures there are no features that exist in the previous version that has been compromised in the updated version.

  • Complete Regression Testing : Complete regression testing is performed in case there are multiple changes done to the already existing code. On completion of this type of testing, the final system is made available to the user.

  • Partial Regression Testing : Partial regression testing is performed after impact analysis. In this testing process, the new addition of the code as a unit is made to interact with other parts of older existing code.

  • Unit Regression Testing : It is an important part of unit testing. Unit regression testing mainly focuses on the code unit and all the dependencies and interactions are temporarily blocked during the test.

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