The Differences and Values of Retesting and Regression Testing

How engineering teams can achieve less retesting and faster regression testing through Predictive Test Selection.

Key Takeaways

  • Retesting aims to ensure that functionality has been restored after a bug fix.

  • Regression testing verifies code changes against existing functionality to ensure new changes don’t impact old code.

  • Teams looking to shift testing less and reduce the amount of retesting benefit from intelligent test selection.

  • Faster regression testing is possible with machine learning, using your own testing data to intelligently select the most critical regression tests to run.

Within DevOps methodology, the software testing life cycle is the second side of the coin to the software development life cycle. Both components are critical to releasing high-quality, error-free apps. 

The pursuit of Continuous Quality relies on dual software testing types: proactive and reactive. Retesting and Regression testing both support this pursuit, but in two very different ways. Both approaches to software testing help a tester find defects as quickly as possible so they don’t derail the release of an app later down the line. They differ most on what they are testing for and how they can be executed. Retesting works to solve known bugs, while regression testing uncovers and spot checks for newer issues. 

Retesting assesses known bugs and whether they are fixed.

Retesting checks specific test cases and is performed to assess known bugs, to see if they were actually fixed. Instead of focusing on previous versions, retesting aims to ensure that functionality has been restored after a bug fix.

Typically, testers find the bugs while testing the software application, then send the problem back to developers to fix. Developers will address the issue, then send it back to the testing environment for verification.

Retesting is always a manual testing process and can never be automated, as it checks for a specific defect and relies on the expertise of your DevOps teams. Retesting is not a guaranteed part of the testing process - it’s only utilized when a bug is found and corrected.

Regression testing checks for unknown issues due to code changes.

You can think of regression testing as essentially a compatibility check. Regression testing is performed when code is changed and after a new feature is added, to see if the change impacts the existing infrastructure. Regression testing might also be done if a flaw or bug is uncovered

Regression testing involves running a full or partial selection of already executed test cases, to assess if the existing functionalities of an app will continue to perform. Regression testing ensures happier customers, as this kind of software testing makes sure new features don’t interfere with old ones. Regression testing can be automated and goes beyond functional tests to ensure quality releases.  

The power of regression testing lies in its ability to uncover new defects before they accumulate. In complex products, regression testing can be time-consuming. 

What are the differences between retesting and regression testing? 

As we mentioned earlier, these test types fall into two categories: proactive and reactive. Consider regression testing as proactive as it is performed on past test cases and is assessing any side-effects after new code changes to find any new issues. Retesting is reactive as it is performed only on failed test cases and is intended to see if existing bugs are solved.

Here’s an easy breakdown of the differences between retesting and regression testing to simplify where they vary.

Regression TestingRetesting
Performed for passed test casesPerformed only for failed test cases
Tests for unintended side-effects after new code changes or featuresTests to see if an existing bug was fixed
Does not include defect verificationIncludes defect verification
Automated testing possibleManual testing only
Finds NEW issuesFinds KNOWN issues

Retesting and regression testing bottlenecks and how to avoid them.

Software testing is critical to the success of a release. However, that does not mean it comes without flaws or bottlenecks.

Retesting requires rework and can bog down pipelines. One significant culprit that can hinder retesting efficiency is flaky tests. Flaky tests are all too common in software testing and can be a result of inconsistency in testing environments, failure to refresh test data between test runs, timing issues, and dependencies on the test execution order. However, flaky tests undermine confidence in testing overall and pose a major roadblock in the CI/CD pipeline.

One of the biggest challenges associated with regression testing is the sheer amount of tests that must be run. As a project becomes more complex, so too must the regression testing. This can eat up the time of developers, especially when coupled with the problems of a growing test suite or constantly changing test suites.

Re-testing: very important. Regression testing: also very important. However! Both kinds of software testing can drag down developer experience without the proper tools.

Less retesting and faster regression testing with Predictive Test Selection.

Launchable helps teams shift left by testing earlier and often with an intelligently selected subset of tests. Our Predictive Test Selection uses machine learning to identify the tests with the highest probability of failing, based on code and test metadata, helping teams intelligently choose the best tests to run. Predictive Test Selection cuts down the amount of retesting needed by identifying the most critical tests to run earlier.

Additionally, Launchable’s Test Insights highlights testing the top flaky tests in your suite so your team can enjoy high levels of confidence in test cases. Flaky Tests Insights tracks increase in test session duration, to identify if developer cycle time is trending upward. Flaky Tests Insights also highlights which tests are being run less frequently, and offers visibility on the tests failing to actually identify and solve any flaws or issues.

Our dev intelligence platform helps developers speed up their testing suites, including regression testing. We specialize in making test suites more reliable and efficient, creating a better experience for your entire development team. Enjoy less retesting, and better regression testing with Launchable.

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