Insights Blog The Complete Guide to Regression Testing


The Complete Guide to Regression Testing

Regression testing is required for the unification of software and is especially important now with so many companies adopting continuous delivery. Here's all you need to know.

Regression testing

One of the most widely used testing types in every software testing project is regression testing. Traditionally, when a system regresses, it means moving back to a former, less developed, or more primitive state.

Essentially, the regression testing process involves testing parts of an already tested application after it undergoes any changes like a new software addition, a feature update, a code change, a defect fix etc.

So, if an application has three functionalities- A, B and C, we make changes only to functionality C. The correct method to now evaluate the whole application would be to test all three functionalities again, along with the rest of the system. This is mainly because we need to see if the change made to C impacts the other functions in any way.

The need for regression testing

With impending production deadlines, fast-approaching time to market and hefty cost constraints, software owners may question the exact purpose of regression testing.

Regression testing is required for the unification of software. The main aim of regression testing is that no existing functionality is impacted due to any latest changes.

So why exactly do we perform regression testing?

The latest changes introduced to the system may have had an unexpected impact on another part of the system because they have interconnected components. So, when we’ve changed a part of it, it might have certain impact on other parts.

Let’s understand why regression testing is essential with an example: An e-commerce application has a signup/registration functionality. When the user clicks on the register button, they have the option to sign up in diverse ways (Facebook/Google/email login). When a particular method fails, it points out a defect in the signup functionality. When the developer fixes this defect, it may affect other parts of the application or other registration methods. This is where regression testing comes in to test the unchanged parts of the application.

The next question that arises is, when do we do regression testing?

The simple answer is pretty much whenever the system undergoes a change. Now, this may sound like a monstrous nightmare to people who think that we do regression testing manually. Given the complex interconnected applications of today, automation is the way to go for performing continual regression tests.

How did the concept of regression testing evolve?

Back in the day, with the waterfall model, complex projects and systems would take years to develop and test. The subsequent defects and unfulfilled requirements led to lengthy development and fixing cycles. In addition, several simultaneous untracked changes and the lack of communication between Dev and QA teams added to the burden.

The result – no impact assessment on the business level and a very risk-heavy approach to development. The test approach was merely fixated on test cases and scripts and was slow to respond to changes.

Regression testing thus stepped in and saved a lot of time by rerunning already identifiable tests.

Types of regression testing

There are multiple ways in which we can perform regression tests.

Some of these include:

Corrective regression testing

A simple form of regression testing that requires lesser effort, this focuses on reusing the existing test cases without changing the testing scenario.

Complete regression testing

This type of testing comes into practice when the root code of the application has been changed and the system undergoes large-scale updates.

Selective regression testing

This testing type selects specific test cases from a group to evaluate the affected parts of the code.

Progressive regression testing

This testing approach is followed when new test cases are designed for updated and modified product specifications, to cater to the changing requirements and altered test scenarios.

Retest-all regression testing

This complex approach needs the entire system to be tested from scratch, even the minuscule changes made at the very beginning.

Unit regression testing

This is a simple approach to regression testing that focuses on testing the code as a single unit. The test coverage is limited to code only and ignores its inherent dependencies, integrations, and interactions.

Partial regression testing

In this approach, separate blocks of the code(modules) are tested using the existing test cases before being merged into a shared code integration.

Regression testing process: How is regression testing performed?

Most QA experts follow the below-mentioned method to perform regression testing:

Detect change -> Prioritize change -> Determine entry point -> Determine exit point -> Schedule test

At first, QA experts detect the changes made to the source code.

Any components or modules modified in the process are identified, including any impacts that the change may have had on other functions.

We then prioritize these alterations and product requirements while streamlining the testing process with the corresponding test cases and tools.

The next step is to set the eligibility criteria and minimum conditions before executing the regression test and finally conducting the test and recording results.

Regression testing techniques

When implementing regression testing, QA experts usually choose among the below-mentioned techniques based on the project’s requirements.

Regression test selection

Testers select the relevant parts affected by the modifications and perform regression testing on only those parts, thus reducing the testing time and effort.

Test case prioritization

Test cases are prioritized based on failure rate, impact on the business/product, and how often the particular functionality (under test) is used. Testers always assign a higher priority to customer-facing aspects of the application and new or updated functionalities.

Complete regression

As the name suggests, in this technique, all the existing test suites are tested. Although it requires more time and effort, it is the best approach when the application undergoes a significant change.

Regression testing challenges and their solutions

Performing regression testing is a complex effort that requires understanding its intricacies. The major challenges with regression testing are:

A time consuming and expensive affair

Regression testing employs costly software testing resources such as time, money and workforce. Testers are under the implication to perform exhaustive testing.

Solution: A QA manager can devise intelligent plans to create a less time-consuming testing schedule by leveraging test automation to adhere to strict time and budgetary constraints.

A complex process

Software products are dynamic; with every added functionality, test cases keep increasing, leading to confusion.

Solution: Prioritizing test cases, monitoring the test suit and deleting obsolete test cases can decrease the complexity of regression testing. All of the above measures can be facilitated by automating regression tests.

Assessing business impact

Communicating the value of continual regression testing to stakeholders is difficult, given the time and resources to make it fruitful. Only testers and developers can understand its true importance.

Solution: Keeping all non-technical stakeholders on the same page and staying within deadlines as specified in the regression test plan is the right approach.

Best practices of regression testing

Given that regression testing takes considerable time and effort, we must follow some guidelines to make these efforts fruitful. Some of these include:

  • Maintaining a consistent testing schedule.
  • Using a reliable test management tool.
  • Breaking down and categorizing tests.
  • Considering customer and business risks.
  • Evaluating test prioritization.
  • Automating wherever possible.

Difference between regression testing and retesting

Regression testing is different from retesting in many ways. Retesting is simply testing a defect that has been fixed. It includes those test cases that failed earlier. The main aim of retesting is to remediate the original issue and ensure the affected feature is functioning as expected.

Retesting is a planned effort performed by replicating the same scenario using the same data but in a new build. In some instances, an entire module must be retested to ensure its quality.

In simpler words, a bug is found by a tester, the developer fixes the bug, and now the tester has to recheck the functionality; this is retesting. Retesting is performed only for failed test cases. There are no adverse side effects of code changes on existing functionality in retesting.

On the other hand, regression testing is more worried about whether the change introduced in the system affects the OTHER/REMAINING parts of the systems. Retesting cannot be automated, while regression tests can be automated.

Another major difference is that, in retesting, only bug fix related test cases are checked, while regression testing covers all types of test cases.

Summing it up

Regression testing, when done wrong, can be a cause of faulty software. In the absence of a dependable regression testing provider, developers often fail to plan or execute complex regression testing strategies.

Regression testing is instrumental to Agile projects. Moreover, it is critical to businesses and brands that want to be technologically assured. Therefore, the role of experienced software testing services, especially a regression testing and test automation provider, cannot be questioned. Choosing a good provider will ensure greater performance and smooth functionalities consistently.


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