Imagine you’ve got a fancy new app that you’re marketing to consumers. You’ve done your market research, splashed out on an intensive marketing campaign, partnered with a few influencers, and even registered a local domain to give your website the widest reach possible.

Only, the first time you update your app, it’s hit with a bug that makes it pretty much unusable. Disaster! Suddenly all that money spent on research, development, and marketing seems like a bad investment, because your reputation is through the floor and trust in your app is non-existent.

If only it could’ve been avoided.

Well, with regression testing, it could’ve been.

If you want to avoid the bad press of bugs and glitches in your software, then regression testing is the way forward. We’re going to take an in-depth look at what regression testing involves, and how to get it right.

What is Regression Testing?

Regression testing a method of software testing. It involves re-executing a series of functional and non-functional software tests in order to check that a change in the software’s code doesn’t affect its functionality.

Many developers consider regression testing to be an integral part of the software development cycle, as it allows for the detection of unexpected faults that have arisen due to necessary tweaks, enhancements, or bug fixes.

When Should You Perform Regression Testing?

Regression testing can be performed under a variety of circumstances:

• A new feature is added to an existing product
• Code is changed to fix errors or bugs in the product
• Changes are made to the user interface (UI) or configuration of software 
• The source code is optimized to improve performance
• A new version of existing software is developed
• Third party systems are integrated with a product

Any instance that would result in a change to the code of a piece of software is usually cause to run regression testing, as it may have altered the way that the software performs.

Regression testing may also be deployed during lengthy development cycles of software (the average software development cycle is estimated to be around 4.5 months). As new code is added during development, regression testing can be used to make sure that existing code still works as the product is built.

Regression Testing Techniques

There are various different techniques that can be employed when undertaking regression testing.

Retest all

This method of testing involves applying regression testing to all available testing suites.

Retesting everything is the safest way to ensure that any defects or bugs are found and fixed. However, it is also the most costly method of regression testing in terms of time and resources.

For this reason, a complete retest is usually only performed when there is good reason to do so, such as after an application-wide update, when a major bug fix is implemented, or when the application is moved to a new platform. 

Regression test selection

This method of regression testing is more selective, with quality assurance teams selecting specific parts of the application to test, based on how likely it is they’ll be affected by the changes.

Performing only a selection of regression tests helps to reduce the time taken and the resources required. This method will often be utilized by teams working on large-scale, complex applications, where the overall number of test scripts will be higher.

Test case prioritization

Test case prioritization involves determining which test cases should be performed first during the regression testing process.

Factors used to determine which cases should be given priority include:

• Feature failure rate
• Business impact
• Security-related features
• Customer-centric features

Corrective regression testing

Corrective regression testing is used when no changes or updates have been made to the source code. It is used to check how current features are performing, and whether they are functioning correctly, so it can be determined whether or not existing test cases can be reused.

If the results of corrective regression testing are positive, then quality assurance teams can be confident that test cases are up-to-date, and can plan for when new code is added.

Progressive regression testing

Progressive testing is based on the acknowledgement that changes to the source code may require changes to the test suites themselves. Testers will therefore update their test scripts to reflect the changes.

Why is Regression Testing Important?

Regression testing is important for ensuring the continued usability of a product, especially one that is already in the hands of customers. Even small tweaks and enhancements to software’s code can have an unexpected knock-on effect across the entire product.

Not only can this cause problems for customers and lead to a negative user experience, but it can also cost a lot in terms of time and resources to reverse. Detecting potential faults before changes are implemented is paramount in reducing these negative effects.

Practicing regression testing aligns perfectly with an agile testing methodology, making it a valuable testing method for developers. More frequent testing means that potential errors are detected earlier, and can be rectified long before the product goes into production.

Image sourced from broadcom.com

Visual regression testing is equally as important as testing functionality. Not only does it help to preserve the visual aesthetic and brand identity of the software, but it also helps identify any misaligned images or unclickable buttons that have appeared as a result of updates to the code. 

For a website, changes like this can be marked up using annotation software such as MarkUp.io, identifying to testers which areas are presenting a problem, without altering the HTML code of the website.

How to Perform Regression Testing

How regression testing is performed will depend on the individual goals and needs of the organization carrying it out. However, there are some fundamental steps that will be present in most instances of regression testing.

1. Detect changes in source code

Firstly, any modifications or optimizations in the source code must be identified. Code review sessions can be conducted in order to determine which components or modules have been changed, and what impact this has had on existing features.

2. Prioritize identified changes

Once all the changes have been identified, QA teams should determine which cases need to be tested extensively, and which require less thorough testing.

The larger the codebase, the more important it is that cases are prioritized. Automation testing can be used to help streamline the process of QA software testing.

3. Select test cases to re-run

Next, you need to determine which test cases are to be re-run. It’s not yet necessary to test the entire test suite. Instead, test cases can be categorized as either reusable or obsolete. Obsolete test cases can be omitted from future test cycles, while reusable test cases can be shortlisted for regression testing.

4. Categorize regression test cases

Once the test cases have been selected, they can be categorized. Common test categorization criteria include:

• Manual vs automated regression tests

Tests which involve repeating the same series of steps over and over again can be performed using automated testing, while it is often better to apply manual testing and human evaluation to non-repetitive cases.

• Testing type

The testing environment, setup, and tools required for each test case can also be taken into consideration, with more easily tested cases prioritized.

• Critical vs non-critical features

The urgency and significance of test cases can be ranked on a scale of low, medium, and high, based on the potential impact to the business and its customers.

Image sourced from guru99.com

5. Prepare the test environment

If you’re undertaking frequent regression testing, it’s useful to have test environments to hand for whenever you need them. Environments need to be stable and ready-to-test, as a poor testing environment increases the likelihood that tests will fail and defects will go unnoticed.

When considering the test environment, it’s worth examining the advantages and disadvantages of utilizing physical devices or a cloud environment.

Manual testing requires setting up and maintaining devices, which will involve collaboration with IT, Ops, and finance, which can make it a lengthy and costly endeavor. However, it may be necessary to test some applications on physical hardware. 

Image sourced from perfecto.io

For example, games need to be tested using components such as graphics cards and  processors in order to properly test load times, rendering quality, and frame rates.

On the other hand, web-based applications could be more easily tested using on-demand cloud environments, helping to reduce the upfront cost of obtaining and preparing physical hardware. 

6. Schedule and execute tests

Once the previous steps have been completed, the test cases should be ready for execution. Tests can be scheduled based on the plan developed earlier, taking into account priority and categorization. 

Time-based test execution provides greater control over software quality, so scheduling tests at intervals across the entire development cycle allows for greater quality control over the constantly changing code.

7. Measure success

Once tests are complete, the process can be analyzed in order to provide valuable insights for future test runs. Applications such as data model tools can be used to assist in visualizing the data obtained from testing, helping to make it easier to digest and analyze.

Reports generated by testing can also help to reveal weaknesses and pain points in the application early, which can then be addressed before they enter production. The earlier a bug is detected, the less costly it is to fix.

Image sourced from blog.pdark.de

Get Regression Testing Right Every Time

So now you know everything you need to get started with regression testing. Identify what you need to test, then prioritize and categorize to make sure the most urgent test cases get checked first.

Make sure you’ve got a functioning test environment ready for whenever you may need it, and investigate ways you can reduce your costs, such as using a cloud environment.

Schedule your tests for the perfect time, and make sure you analyze the results when you’re done.

Follow these tips, and you’ll be identifying and fixing problems left, right and center. 

Photo by Christina @ wocintechchat.com on Unsplash