A Complete Guide To Regression Testing

What is Regression Testing ?

Dictionary meaning of the word "regression" is "the return to a former or less developed state." So, testing done with the aim of catching any regressions in an already tested functionality is called Regression Testing.

These regressions in the code can occur as a result of “bug fixes”, “new features added to the code” or “changing requirements”. The aim is to test all the code that could be impacted due to recent changes to ensure that no new bugs are introduced in an already tested functionality.

Iteration in regression testing

Regression Testing Fundamentals

Regression Testing is the most important kind of testing done when additions or changes are being made to a fairly stable software What are some key points that need to be understood before going ahead with Regression Testing? Let’s find out:

regression testing fundamentals

Regression Testing is done to stable features and functionalities that are tested before a new change is introduced to an application

More the number of changes introduced in an application, the more the chances of finding a new bug in a related functionality

Regression Testing means the execution of already created test cases for a released feature

In an ideal condition, a complete suite of test cases should be executed after every change

In the real world, where time is always a constraint, impact analysis is done to ascertain the areas that may be impacted by a change

To further reduce the time taken by regression testing, sometimes, high priority test cases are executed and low priority test cases are left out

To save on time and resources, experts suggest automation of regression test suite. Most of the software companies worldwide now invest in automation of regression test suite early in the software development cycle.

What Do We Do In Regression Check?

A regression check is usually done after some new changes are done in a fairly stable application. It includes:

Regression check in automation

Impact analysis to decide what areas of the previously stable code needs to be tested for any regression or newly introduced bugs because of the changes

Selection of test cases from already created ones testing the impacted code, based on time allotted for testing and the priority of the test cases. The test cases with higher priority are given more importance

Execution of the selected test cases based on priority. High priority test cases are executed first because the failure of these test cases will be critical and such failures will have to be fixed immediately

Reporting any issues found while performing regression testing

How To Perform Regression Testing?

Regression Testing can be manual or automated. If the number of test cases are small in number, it can be managed in less time manually too but if the number of regression test cases is large, automated regression testing is the ideal solution. The goal is to automate the regression test suite here.
All the test cases that were created for stable features are added to the regression test suite.

When automated, all the test cases added to a regression test suite can be executed after every change as the
testing will be automated and the time taken would be less too.

Following are the steps to follow when Regression Testing is not automated:

  • Understand the changes done in the code. Change may be in the form of a bug fix, a new feature, a new functionality, a minor tweak or a major change in the project requirements

  • According to the change done in the code, analyse and decide what functionalities could be impacted

  • According to priority and functionalities, decide the test cases that need to be executed for regression testing

  • Execute the selected test cases via an automation testing tool or manually

  • Send a report where PASS/FAIL status of all the test cases is clearly conveyed. Also, report all the failed test cases

How to perform regression testing

The Importance of Regression Testing

Regression Testing aims to uncover any bugs that may have been introduced in neighbouring areas of the code when a change is done on one feature.
Often, enough importance is not given to regression testing but there are instances when a major functionality breaks
because of a minor, seemingly harmless fix in an unrelated area.

Regression Testing is important because it is the means to uncover any new bugs introduced in any area of the application after any new changes are introduced to the code. A thoroughly executed regression testing instills confidence in the overall quality of the application before release for the team
members and translates to customer’s trust in the application after release.

Though every kind of testing is important in one way or the other, Regression Testing is the most important just before an application is deployed on production.

Below are the reasons:

quality control

Goal here is to catch any bugs that could have been introduced because of the change before they reach the customer. Thus, we can say regression testing is an example for the saying, “a stitch in time saves nine”.

stakeholders

A PASS/FAIL report is sent to all the stakeholders detailing all the test cases after a regression check. This makes the stakeholders confident about the quality of the product before release.

customer trust

A thoroughly done regression testing also means that customers will have a fully functional product to use without minor or major bugs that could have been introduced by changes in different areas of the code. This builds customer trust and gives them confidence to keep using the product.

  • When the code base for the product is huge and, there are a lot of test cases that need to be executed for regression testing, automated regression testing saves precious time, effort and resources that would otherwise be spent on manual testing

  • Automated Regression Testing reports any errors quickly in a matter of a few hours, which would otherwise take days if tested manually

  • When done manually, humans could skip some test cases. This could be because they are new to the functionality, or there is not enough time for the following steps, or just due to genuine mistakes. Automation makes sure no minor functionality is missed out.

  • To save time, manual testers may have to limit the test cases executed to high priority ones, while all the test cases that are automated can be run any number of times, often after every single change. Thus, the quality is checked at every moment.

During the development phase - developers, testers and the stakeholders are worried more about the quality and correctness of new functionalities being worked on and not so much about the existing functionalities that were thoroughly tested and stable.

But, more often than not, customers would still be using the existing functionalities much more than the new ones.

Developers, certainly, work on a new piece of code when working on new functionality but they are supposed to integrate it with the existing system and make any necessary changes in the existing code to make sure everything works well. During this time, it is highly likely that there could be some functionality in the existing code that might have been broken.

Hence, to make sure customers get the same experience with the product as they were getting even before the new changes were pushed, regression testing needs to be executed.

Anyone who has worked as a Software Tester for even a few years will vouch for the fact that regressions are more common than people generally think. There have been cases when developers were sure their fix has been localized and tested and did not need any more regression testing and later learnt that the same fix introduced an issue in a remotely related feature.

The real question is, how much regression testing is actually required? How to strike a balance between overdoing it and not doing enough?

There could be 2 solutions:

  • If all the test cases in the regression test suite are automated, then this suite can be run from time to time, preferably after a certain number of changes, because running them after every change could amount to unnecessary test execution.

  • If the test cases in the regression test suite are not automated, they will have to be executed manually. When the application is a big one and has a good number of test cases added to the regression test suite, the decision to execute all of the test cases after every change will not be the best solution.

  • There could be multiple approaches that could be adopted according to the need of the project and focusing on the optimum use of resources:

    1. Have the regression test suite ready and decide how much time the complete execution will take. Execute this regression test suite after all the changes are included and tested functionally and the next thing to do is release! Of course, this is not a solution if quick deployments need to be done after a few fixes.

    2. After a fix - a bug fix, a new feature integration or some change in the requirements, do an impact analysis of the change. And according to the change and the time allotted for regression testing specific to that fix, execute the high priority test scenarios.

Regression testing is the most important testing to do before a release to the market or a deployment on production and we have discussed the points above, but of course, it can’t be important without any benefits to talk about.

Below listed are the benefits that people need to know before they brush off regression testing under the rug:

  • The bugs that might come to the product owners after the product hits the production environment, after a well-executed regression testing will most likely be specific to the real-world environment.

  • When a product, after functional and regression testing, gets into the hands of a customer, the experience is much better than the ones where the customer has to face any minor or major issues and keep reporting them. This keeps the customer’s temper at bay most of the time.

  • When a bit of regression testing is done after every small or big fix that goes into the product, there are no surprises left for later and it saves precious time and cost.

  • When the regression test suite is automated, it saves on regression testing time every time there is a fix as it can be run as and when needed any number of times.

Regression Testing Techniques

According to the type of project and its needs, different regression testing techniques can be employed as listed below:

Regression testing techniques

Types Of Regression Testing

Experts have tried to come up with as many as 7 types of regression testing, but, on a broad level there are only 2 types of regression testing:

Complete Regression Testing

Complete Regression Testing:

This is when a complete regression test suite is executed. There could be multiple scenarios in which this is done:

  1. The complete regression test suite is automated and could be executed frequently after any change

  2. There have been multiple changes introduced to the system that were not regression testing because complete regression testing was planned for later when all development work was done.

  3. There were changes in requirements or functionalities that did not require any changes in the existing test cases.

Partial Regression Testing

Partial Regression Testing:

Test cases could be selected on the basis of impacted areas and priority. The selection criteria and a number of test cases executed usually depends on the availability of resources including time. This can be done in multiple scenarios as listed below:

  1. When there are localized changes made to the application and don’t need complete regression testing.

  2. When the project is such that deployments are made quickly after fixes and need partial regression testing to be done to save time.

Read about these in detail here .

Who Should Perform Regression Testing?

new testers

Testers who have not tested the feature before but are capable of executing the documented test cases. In such cases, the documentation should be up to the mark for newbies.

Major bugs

Testers who may not have executed the functional tests but have good knowledge about the features that need regression testing and can catch any major bugs, if any, introduced in them.

old testers

Testers who previously executed the functional tests for the features that need to be regression tested.

How to Implement Regression Testing

Before implementing Regression Testing in an organization, it is essential to analyse what kind of processes are being followed. Rather than changing the complete process to include regression testing, the recommended approach will be to find ways by which regression testing can be made a part of the process seamlessly.

Below is how the different types of regression testing can be applied in different processes that we saw above:

Complete Regression Testing

Complete Regression Testing:

If the Software Development and the Testing processes are such that there are a lot of bug fixes going on at the same time, doing partial regression testing after each fix will prove too much time taking. Then performing complete regression testing once all the development work is done makes more sense.

Partial Regression Testing

Partial Regression Testing:

If the Software Development and Testing go hand in hand and the deadline cannot be extended, it is better to do partial regression testing after every change such that additional time is not needed before the release, especially for regression testing.

Automated Regression Testing

Automated Regression Testing:

Works best if the project being tested is not a one time project and is going to be around for a while. Also, if the project has quite a big regression test suite. It is recommended to invest time in the automation of the regression test cases to save time spent on executing the regression test suite manually multiple times.

Regression Testing vs Functional Testing

While Regression Testing makes sure that there are no regressions in a product in related areas after a bug fix or a change, functional testing ensures the functionality of a product is according to the requirement specifications.

Regression Testing can include both functional testing and non-functional testing.

Usually, it is the test cases created during functional testing that are included in the regression test suite once the functionality being tested becomes stable. So, eventually functional testing becomes a subset of regression testing.

Regression testing vs Functional testing
Why Should Regression Testing Be Automated?

Why Should Regression Testing Be Automated?

If you have a product that has a big regression test suite and is under active development, the best advice will be to automate the regression testing. Reason being, Regression Testing is the only kind of testing that needs to be repeated multiple times.

It could be before every release when complete regression testing needs to be done or it could be after every change is done to the code, in the form of partial regression testing.

Automated Regression Testing Tools

There are many tools that can be used for automation of regression test suites, few of them are listed below:

testsigma

Testsigma

Uses simple English words to automate complex tests. Testsigma is an ideal tool to automate regression tests with suggestions of affected test cases. Check out more about Testsigma's approach to automated regression testing .

Katalon

Katalon

This tool has an IDE called Katalon Studio that supports creation of test cases in JAVA and Groovy. It also has a Katalon Recorder that can be installed as as extension to browsers and can be used to convert recorded steps into code in a preferred language( C#, JAVA or Python) which can be further enhanced according to the needed complexity.

Selenium

Selenium

This is a free tool for automation of workflows on websites

Ranorex

Ranorex Studio

Has options for record and play as well as automation in a programming language.

How To Select A Regression Test Suite?

A regression test suite is a collection of test cases that should be executed when regression testing needs to be done. But as there are different
types of regression testing adopted by companies depending on the processes they follow, there are also different types
of regression test suites that should be created according to what is needed:

Complete Regression Testing

Complete Regression Testing:

When complete regression testing needs to be executed, it is usually done after all the development work has been completed. For this, the regression test suite should contain all the test cases that were created during testing for all the features that were added and also the integration test cases.

Depending on Time availability - high priority and low priority test cases can be selected for execution.

Partial Regression Testing

Partial Regression Testing:

If aim is to do partial regression testing, then test cases will have to be decided according to the change after which the regression testing needs to be done, the test case selection should be based on:

  1. Test cases for the functionalities that are impacted

  2. High priority test cases are executed first to catch and report any high priority issues at the earliest

  3. Sometimes, depending on time availability, only high priority test cases are executed for impacted areas

Automated regression testing in Agile : why, what, and how ?

When software development is done following agile methodology, new changes are pushed to the product every sprint and the expected output for
a sprint is supposed to be a working deliverable. This means that the product should be tested and working in each and every sprint.

Hence, after all the changes the product’s regression testing will be important at the end of every sprint.

Automated regression testing in agile

If the regression testing at the end of every sprint was supposed to be done manually, it will eat up a lot of time and resources. Thus, automation of the regression test cases will play a very important part in saving the time and keeping the quality of a product consistent every sprint.

During automation, what needs to be automated needs to be decided with utmost care. The high priority test cases should be automated first starting with the automation of smoke and sanity test cases. And, also, if there are some areas of the product that are prone to changes and are not stable yet, the changes should be avoided.

The automation should be done using a tool that supports the automation of regression test cases.

Why is automated regression testing so challenging in Agile?

Agile focuses on software development and testing in iterations. Software Development can be done in iterations because that just
means adding more code for the functionalities but the real challenge is for testers because they also need to ensure:

To ensure great quality of the product at the end of a sprint, testers have to make sure that the automated regression testing is able to execute successfully on all the impacted areas of the code.

The number of changes that go into the product during the sprint and the probability that these changes could also break some of the automated test cases makes it more challenging in the agile mode. Thus, maintenance of the automated test cases should be considered the most important.

Challenges faced during the automated regression testing are:

What can you do to make automated regression testing of the UI economically feasible?

For the automated regression testing of the UI to be economically feasible, there are few points
that should be considered before automation is put into place:

Scriptless automation testing of UI regression testing

There are many applications that have an elaborate UI and need UI regression testing to be automated for best performance at all times. There are many automated testing tools that offer scriptless automation of UI regression testing. Some of the tools are:

Selenium

Selenium - record and play feature can be used here to achieve codeless automation

Sikuli

Sikuli - Python-based GUI automation tool, uses image recognition algorithm for element selection

Katalon

Katalon - very similar to Selenium, and its record and play feature can be used to achieve codeless automation Automation should only be preferred when there will be an ROI in the long term because of this automation of applications that are supposed to have active development and maintenance for a long time are preferred

testsigma

Testsigma - An ideal automated regression testing tool that suggests relevant or affected test cases after a feature enhancement/bug fix. Testsigma lets you run regression tests right after the first check-ins, automatically, within a sprint.

SeeTest

SeeTest - A mobile automation tool that supports image-based as well as object-based recognition

test.ai

Test.ai - AI-powered bots that generate and execute test cases for testing UX of a mobile application.

Regression testing in an agile context : basic concepts

  • Because every sprint in agile needs to have a working deliverable as its output, regression testing to ensure nothing that was working before has broken is essential

  • Regression testing can be done manually if the application under test is new and there are not many functionalities to test yet. But if the number of test cases in the regression test suite has increased to a significant number, it is advisable to automate these test cases, to save time and efforts in the long run

  • Not all regression test cases need to be executed after every change, testing of impacted areas should be given priority when only limited time is available

  • High priority test cases for the impacted areas should be executed for smart testing that also saves time and effort

Regression testing in agile
Automated regression testing key considerations

Key considerations for automated regression testing

  • Before deciding for automation, a proper analysis should be done for the cost of automation and if that will have an ROI in the long run. If the project is such that once it is released, the amount of testing and development will be negligible, the automation will prove to be a waste of time and resources.

  • If regression testing is decided to be automated, automation of only those test cases that are stable and passing should be targeted. This saves any unnecessary time spent in troubleshooting a test case and prevents any wrong assumptions about the test scenarios

  • Not all test cases need to be automated. Start automating test cases according to priority. Like, automate the high priority ones first and then move to lower priority ones. If there are test cases that will rarely be executed in the real world, leave them out.

Why is regression testing important in agile development?

Agile development focuses on development in iterations, thus testing is also done in iterations. But, the end result for each of these iterations is a working deliverable. To be able to have a working deliverable at the end of every sprint, it is essential to do regression testing before the end of every sprint.

Regression testing challenges faced by agile teams

  • Execution of the regression test suite is needed at the end of every sprint

  • The regression test suite needs to be updated every sprint with the test cases for the functionalities that are now stable.

  • All the test scenarios that changed during the sprint should be automated

  • All the test cases should be prioritized on the basis of importance

  • During regression testing, test cases should be selected on the basis of areas impacted and executed based on priority

  • Regression Testing should be time effective to make sure the end goal of the sprint in agile methodology is achieved.

Importance of regression testing in Agile

Regression Testing: Strategy, Framework, and Best Practices

According to the type of project, regression testing strategy can be decided. Example: If the project has a lot of development work going on in parallel, it will be a good idea to do a regression test once all the development work is completed. If the project is such that there won’t be much time for regression testing at the end, regression testing will have to be executed after every change. Here, selective regression testing will be needed, for which:

Framework will have to be defined for regression testing keeping below points in mind:

Best Practices for achieving best results are:

FAQs on Regression Testing

What is the objective of regression testing?

Whenever there are some changes introduced to some part of the code in the application under test in the form of bug fixes, enhancements, changes in requirements or features, there is a probability that some functionalities in the related areas of the code could be impacted.

Thus, the objective of Regression Testing is to make sure that the features and functionalities, that were tested to be stable before a change was made in code, continue to be stable even after the changes.

When performing regression testing, should I follow the steps strictly or deviate from the steps?

Regression Testing could be automated or could be performed manually depending on what processes are adopted by an organization for a product. If automated, the regression testing will necessarily be performing the same steps again and again.

But if done manually, the testers can use common sense to not repeat the same steps for all the test cases and try variations of it to uncover any new bugs.

Can regression testing be automated?

Regression Testing can surely be automated. To proceed with automation make sure below 2 conditions are met:

  • Application under test is planned to be under active development for a long time

  • The number of regression test cases for the application under test are quite a lot such that it will take a long time to execute manually.

How much regression testing is enough?

If the regression test cases are automated, much time won’t be lost even if all the test cases were executed. Thus, in such a scenario, how much regression testing does not need to be thought about.

But, if the test cases are not automated and time is a constraint - which usually is - the best way to go about it by following below steps:

  • Analyse the change and the impacted areas because of the change

  • For the impacted areas, execute high priority test cases

  • For the application as a whole, execute the critical test scenarios before any deployment or release

What if there is no time for regression testing?

Regression Testing is absolutely essential to minimize the number of issues reported by customers post release. But there are times when the managers and stakeholders don’t realize the importance of regression testing and thus, don’t assign the time for it.

Being a tester, below are few things that can be done:

  • Discuss the importance of regression testing with your management and project stakeholdersWith every change testing - try to execute at least the critically important test cases for impacted areas.

  • Before every release - create a release checklist that includes execution of the most important workflows that a customer will go through for sure.

  • When possible, automate the regression test cases.

What is regression testing automation?

During the SDLC(Software Development Life Cycle), features are added to a product incrementally. Once a feature is tested thoroughly and is deemed stable, the test cases created for the testing of that feature are added to the regression test suite that will be executed when further changes will be made in the application in the future.

The test cases in the regression test suite can be easily automated as these are stable and the process of automating them is called regression testing automation.

What are the advantages of regression testing automation?

  • When the code base for the product is huge and there are a lot of test cases that need to be executed for regression testing, automation saves precious time, efforts and resources that would be spent on doing the testing manually otherwise.

  • Automated Regression Testing reports any errors quickly in a matter of hours which might have taken days if the testing was done manually.

  • When done manually, humans could skip some test cases because of being new to the functionality or shortage of time or just by genuine mistake. Automation makes sure no minor functionality is missed.

  • To save on time, for regression testing, manual testers decide on test cases according to priority while when automated all the test cases that are automated can be run any number of times, often after every single change. Thus, the quality is in check at every moment.

Why is regression testing automation required?

Regression Testing involves execution of test cases corresponding to stable features and functionalities for an application. These test cases need to be executed multiple times, sometimes after a change in the code in the form of bug fix, enhancement, new feature, change in requirement.

Because these test cases need to change rarely and are executed multiple times during the SDLC(software development life cycle) for a project, they become a perfect candidate for automation

Why is regression testing automation important in Agile software development methodology?

Agile development focuses on development in iterations, thus testing is also done in iterations. But, the end result for each of these iterations is a working deliverable. To be able to have a working deliverable at the end of every sprint, it is essential to do regression testing before the end of every sprint.

Is regression testing automation part of DevOps?

There is no right or wrong answer to this question.

There are organizations that don’t give so much importance to testing as compared to the speed of deployment and thus there are times when regression test automation is not a part of DevOps. But, even then there are organizations that have understood the part that regression testing plays in maintaining overall quality of a product and thus, have integrated it into their DevOps.

Now, as people are becoming more and more aware about maintaining quality of an application, experts are advising companies to include regression test automation under DevOps to enhance quality feedback loop.