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What’s the Difference between Retesting and Regression Testing?

21 mins

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Retesting and regression testing are frequently confused with one another. While both types of software testing are conducted later in the development lifecycle, they are fundamentally different in purpose and scope. Both are a part of quality assurance services that offer crucial benefits to the project’s ongoing success.
Continue reading to learn the key differences between retesting and regression testing. Explore example test cases to see how these tests improve application quality, discover quality tools, and better understand the benefits, requirements, and scope of work. Finally, see how SumatoSoft can deliver the retesting and regression testing services necessary to ensure success of custom software development.

Retesting

What Is Retesting?

Retesting ensures that efforts to fix a bug in a system have been successful. Developers and IT professionals will always retest the functional or non-functional testing they used to diagnose that issue.

A key difference between retesting and regression testing is that retesting is not broad in scope; the objective is to test for a specific bug that developers already know exists and believe to have addressed. For this reason, retesting is unlikely to reveal previously undiscovered bugs unless they arose directly from efforts to fix the issue currently being retested.

Types of Retesting

types of testing

Retesting covers all types of functional and non-functional testing. A retest could effectively be any type of software testing. It refers instead to repeating the test they used to find the bug in the first place.

Developers often retest both functional and non-functional types of software testing, including:

Functional Testing

  • Acceptance Testing – Clients test the software in real-time usage environments, including alpha testing and beta testing
  • Integration Testing – Identifying bugs in the communication, data flow, and interface of individual modules as they are integrated into the full system
  • System Testing – Testing the full system against specified requirements, including black box testing, end-to-end testing, happy path testing, monkey testing, sanity testing, and smoke testing
  • Unit Testing – Testing individual system units in isolation, including gorilla testing and white box testing

Non-functional Testing

  • Compatibility Testing – Assessing the system’s compatibility with various hardware, network environments, and servers
  • Performance Testing – Assessing response time and stability under load simulations, including endurance testing, load testing, scalability testing, stress testing, and volume testing
  • Security Testing – Performed by hacking teams to identify vulnerabilities in system security, including penetration testing
  • Usability Testing – Assessing user experience, including accessibility testing, cross-browser testing, and exploratory testing

When do You Need to Perform Retesting?

As we’ve stated, retesting is almost always necessary when another test identifies a bug or performance issue. However, you may also need to retest previous assessments in other scenarios:

  • When you encounter issues with the software suggesting a bug that previous tests may not have detected
  • When you update or replace existing functionalities
  • When the application is deployed, graduating from simulated testing environments into real-world usage
  • When users report bugs or insufficient performance
  • When the standard load or circumstances of the software change, perhaps due to changing business capacity or infrastructure
  • When issuing upgrades to the application or its corresponding documentation

While retesting is necessary to ensure that bugs have been fixed, you may wish to retest some outcomes before attempting those fixes. Retesting with a narrower scope may offer greater visibility into the underlying issue, better equipping developers to achieve successful outcomes.

The Scope of Work for Retesting

testing planning

The scope of retesting work depends on the number and scale of the bugs detected during the testing stage. A difference between retesting and regression testing is that retesting will typically benefit from a narrower scope of work than regression testing, as the scope is narrowed by your team’s awareness of existing bugs.

The Benefits of Retesting for the Project and Business

Ultimately, retesting improves the quality of the product, both before and after it reaches the market. This presents a few meaningful benefits for both the project development team and the business or businesses that will use the application. The biggest benefits of retesting are quality assurance and testing efficiency, as we outline below.

Quality Assurance for Developers and Clients:

As a part of a quality assurance plan, retesting validates the efforts of developers to correct application shortcomings, creating peace of mind for both the development team and end users. For development teams, retesting mitigates the need for ongoing support by verifying that known issues are fixed. For users, retesting serves as a confirmation of adequate performance.

Focused, Streamlined Testing Procedures:

Most software performance testing is broad in scope, attempting to account for any potential risk and view the application performance holistically. This can be time-consuming, labor-intensive, and expensive.

Retesting narrows the scope by building off prior testing efforts and homing in on specific issues that developers already know exist, helping them save resources and navigate the testing process more efficiently. Additionally, retesting does not require the setup of new testing environments and data, as it repeats existing testing environments to compare outcomes.

Retesting: Test Case Examples

Retesting Example #1:

A software development company is building an application for a company to aggregate client data based on numerous business parameters. This application allows users to filter historical client data to create reports and forecast outcomes.

All these filters work as intended except for one filter that allows users to specify a date range. The filter always includes data up to the current date, regardless of the date entered. A tester reports the error during the functional testing process and raises it to the development team. The development team assigns the bug to a developer who finds the fault in the application’s coding and fixes it.

The functional test that identified the bug is then repeated to ensure the fix was successful.

Retesting Example #2:

A software development company is building an online customer portal that will allow a business’s customers to access their account information.

As the testing team conducts a stress test, the application crashes when confronted with a number of users only slightly larger than the expected average capacity and well under the expected peak capacity. The expectation was that the application would be able to manage a substantially higher user capacity than testing indicates, so a member of the development team is assigned to address the issue.

The tester may apply additional performance tests or even retest the stress tests to learn more about the cause of the issue, then retest again after fixing it.

Regression Testing:

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What is Regression Testing?

testing process

According to Merriam-Webster, regression is defined as a “trend or shift toward a lower or less perfect state,” which aptly applies to software testing.

Regression testing refers to tests conducted to ensure that an application continues to perform to the standards it met when it went to market. It ensures that new features and updates have not negatively impacted application performance in unforeseen ways.

Regression Testing: 7 Types in Software Development

Regression testing can be conducted in any of the following seven ways:

Types #1: Complete Regression Testing – Complete testing is used specifically when multiple updates or changes have been made to the application’s root code.

Types #2: Corrective Regression Testing – Testing teams use corrective testing when no updates or changes have been made to the application, allowing them to use re-use existing test cases.

Type #3: Partial Regression Testing – When updates are made to an application’s existing code, testing teams will use partial testing to ensure the new code has not disrupted application performance.

Type #4: Progressive Regression Testing – Progressive testing refers to circumstances where changes to the system specifications require that new testing environments or cases be developed.

Type #5: Retest-all Regression Testing – The most comprehensive form of regression testing, retest-all testing reuses all previous test cases for a full comparison with previous testing outcomes.

Type #6: Selective Regression Testing – Selective testing isolates a specific subset of a previous test case, saving time and resources while assessing the impact of a code addition or update.

Type #7: Unit Regression Testing – Units of code are tested in isolation from their respective dependencies.

Regression Testing: When You Should Run and How Frequently

Developers typically run regression testing when updates or upgrades to existing functionality are implemented, either before or after those changes are released to the market.

Periodic releases, usually either weekly or monthly, often call for regression testing as part of their regular testing cycle. Unlike retesting, which is conducted in response to finding a bug, regression testing is conducted to see if such bugs exist. Because regression testing is pre-emptive rather than reactive, it is usually conducted periodically.

A difference between retesting and regression testing, however, is that regression testing maintains the scope of past testing, conducted to ensure that outcomes remain consistent with (or superior to) previous test cases, even when changes have been made to the application.

Defining the Scope of Regression Testing – How Not to Overrun Your Budget

meeting on testing

Regression testing is an ongoing expense for active applications, making it time-consuming and potentially expensive. 72% of midsize and large enterprises in the USA rely on automation to better manage costs and resources.

Automation vastly broadens the potential scope of work for regression testing but setting up automation infrastructure can itself be costly and disruptive. Manual regression testing is a less scalable option but comes with much lower costs upfront.

Either manually or through automation, the scope of regression testing work is primarily defined by the scale of the updates or changes affecting those systems.

Regression Testing: Benefits for The Project and Business

The primary purpose of regression testing is to provide QA and development teams with the advantage of visibility into application defects. That advantage can be explained in a few meaningful ways.

Ongoing Quality Assurance Across the Full Development Life Cycle

Regression testing provides an ongoing holistic view of application performance, even as new updates and features are factored into the code.

Those new features can better align with existing systems to minimize the risk of defects or even crashes, ensuring sustained quality across the life of the product. Regression testing creates a more comprehensive visibility of risk in the development cycle.

The result is a higher level of confidence in the project for the customer and a lower risk of support expenditures for the development team.

Provides a Framework for Continuous Performance Testing

Regression testing can often be (and often works best when) automated. With repeatable test cases and a testing infrastructure that supports continuous testing, development teams can be more agile and efficient and respond earlier to defects. This protects the development team and potentially also the customer by minimizing the number of defects that impact the performance of the business.

The Best Regression Testing Tools

tools

The availability of tools is a key difference between retesting and regression testing. Retesting is repeat of another type of testing, and thus will use that testing tool. Regression testing, however, can be automated via several quality tools, some of them open source.

  1. Apache Jmeter – An open-source testing automation software that measures test performance against a set of functional test behaviors.
  2. IBM Rational Functional Tester – This powerful, comprehensive testing tool automates regression testing to deliver rapid, detailed responses and extensive functionality.
  3. Katalon Studio – A regression testing tool with an accessible interface, making it a great fit for testers of all experience levels. Offers end-to-end testing automation and supports running scripts across a wide range of environments.
  4. Sahi Pro – A great regression testing automation tool for cross-browser or multi-browser testing. Sahi Pro is considered a particularly tester-friendly tool.
  5. Selenium – Another open-source testing automation tool for web applications, supporting several browsers and platforms, broken down into a set of four manageable tools.
  6. TestComplete – A powerful and flexible regression testing automation tool that works across a wide range of devices, platforms, and scripting languages.
  7. Watir – A suite of open-source automation tools that primarily work on a Ruby library.

Regression Testing: Test Case Examples

Regression Testing Example #1:

An eCommerce business has developed an application to create attractive thumbnail images for their products. They conduct performance testing with over 1,000 test cases before releasing the application to market.

Later the client requests additional features from their development company. The developers add the new features to the app code and then conduct regression testing to ensure the new features have not caused defects anywhere in the system. The regression test cases are measured against the previous test cases and reveal limited functionality in other areas of the application. The developers find the cause of the problem, fix it, and retest to ensure their fix is successful.

Regression Testing Example #2:

After one year on the market, developers of an eCommerce app compile user feedback to develop and issue the app’s first scheduled update. This update includes improved functionality at the checkout screen for online shopping carts.

Regression tests ensure that the update does not impact the existing functionality of the checkout screen but discover that the application now crashes when multiple users engage in the checkout process simultaneously. Developers correct the data’s impact on the application’s capacity, then retest to ensure the update is successful.

Regression Testing: The Role of Automation

automation

As the user demands for web applications and software continue to grow, the scope of testing must grow with it. This means that manual testing has become increasingly time-consuming and labor-intensive.

Automation is necessary to ensure the scalability and accuracy that regression testing requires. With a regular testing schedule and fully adopted testing too, you can organize a full suite of tests, adding new tests to account for each defect you uncover.

What are the Differences Between Retesting and Regression Testing?


While you may not see many differences between retesting and regression testing, they play equally important yet distinct roles in the development process.

Retesting Regression testing

Conducted with no awareness of existing defects.

Conducted to check for the persistence of known defects.

Conducted to identify any potential defects as a result of the latest code changes.

Conducted to ensure that a known defect has been corrected.

Does not include verification of defects.

Includes verification of defects.

Conducted for test cases that have passed.

Conducted for test cases that have failed.

Considered a form of generic testing

Considered a form of planned testing

Can be automated, as well as conducted manually.

Must be conducted manually.

Can be conducted alongside retesting, depending on available resources and the nature of the project.

Typically considered a higher priority than retesting, and thus often conducted first.

Regression test cases are available before testing, from defect reports, user manuals and tutorials, and specifications.

Test cases are unavailable before testing.

Conducted on code that had been working but may no longer be due to new features.

Conducted on code that had not been working but may have been fixed.

Retesting and Regression Testing with SumatoSoft

The SumatoSoft company uses an agile software development approach. It means that testing, regression testing, and quality assurance become a part of the development process. The development flow is divided into iterations called “sprints”. Depending on the project requirements, we run various tests at the end of every sprint and before the final release. The goal is to ensure that the software provides enough value to be released. 

We have more than 120 successful projects in various industries like eCommerce, Elearning, Finance, Real Estate, Transport, Travel, and more. We provide expert testing services, and these numbers prove it:

Get in touch with our QA professionals today to discuss your project and learn more about our retesting and regression testing capabilities for your business.

Make Retesting and Regression Testing a Part of Your Software Life Cycle

testing software

As you can see, the differences between retesting and regression testing are subtle but important. They combine to play a crucial role in quality assurance for software development. They serve to illustrate the ongoing role that testing, and quality assurance can play. Together, retesting and regression testing help to maintain optimal performance.

While you can be sure that retesting and regression will be necessary for most applications, the challenges of those tests will be unique. Test cases must be designed, data analyzed, and insights actioned by experienced testing professionals.
The SumatoSoft QA team has experience with applications across a wide range of industries and functions. We’ve worked with retesting and regression testing for 10 years. We know what issues to expect and how to solve them. We’ll work with you to understand your business challenges and goals and ensure your applications continue to perform as you need them to. We look forward to hearing from you.