The Simple and Complete Guide on Non-Regression Testing

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A developer’s code changes may impact the software’s functionality.

Even minor changes can have unanticipated consequences or result in the appearance of new bugs. For example, we use regression testing to detect newly discovered problems.

Regression testing is the process of re-running tests to ensure that code changes do not affect existing functionality.

There are times when there isn’t enough time or resources to run regression tests. A testing team can only examine the system modules modified. They do not perform complete regression testing. This is known as non-regression testing.

Non-regression testing is a technique for determining whether a new or modified functionality works properly while assuming that the previous functionality was unaffected.

For example, when using non-regression testing, testers examine only the evolving unit or module rather than the entire product, saving resources and time.

What Is Non-Regression Testing?

Non-regression testing is a technique aimed to verify whether a new or modified functionality operates correctly with the assumption that the previous functionality wasn’t affected.

For example, when applying non-regression testing, testers check only the evolving unit or module instead of the whole product, thus, saving resources and time.

Steps of Non-Regression Testing

#01 Establish a benchmark software release;

#02 Define a set of routines capable of stimulating as many software functions as possible.

#03 Run these routines on both software (the benchmark and the new release under test) and collect data that reflects their behavior.

#04 Analyse this data using a post-processing tool to produce statistical results.

#05 Report the outcome.

#06 Exploratory testing follows similar steps to non-regression testing but differs in its analysis phase and focus, resulting in different results and conclusions.

The non-regression testing goal is to see if any undesirable behavior emerges following the most recent software modifications.

There, the new application behavior is previously known, allowing the identification of an eventual regression (bug).

Exploratory testing, on the other hand, aims to discover how the software works, balancing testing and learning and encouraging testers to create new test cases.

Regression and Non-Regression Testing

While regression testing aims to ensure that a software bug has been successfully corrected by retesting the modified software, the goal of non-regression testing is to ensure that no new software bugs have been introduced after the software has been updated.

In general, this disparity in definitions can be assumed to be based on the results of each test.

When a new software version is released with no new features compared to the previous version (i.e., the differences between the two versions are limited to bug fixes or software optimization), both releases are expected to have the same functionalities.

In this case, the tests performed on both versions are not likely to produce different results but rather ensure that existing bugs have been fixed and no new bugs have been introduced. This testing methodology distinguishes regression testing.

On the other hand, if the new release includes new features or improvements that cause the software to behave differently, the tests performed on the previous and new versions may yield the following results.

Desired differences associated with expected new behavior, and undesired differences, indicate a software regression caused by a side-effect bug.

Also Read: Retesting vs Regression Testing

Regression Testing Vs. Non-Regression Testing

A regression test is typically a test that is we perform to ensure that the system’s various functionalities are still working as expected and that the new functionalities added did not break any of the existing ones. This could be a combination of API/UI/Unit tests run regularly.

Non-regression tests can refer to various things depending on the context of your projects, such as Smoke Testing or Unit Testing that are run during every code check-in.

It could also refer to story-level testing carried out when a specific feature/requirement in a story is being tested. Security testing, load testing, and stress testing may also be performed during the development lifecycle.

How Non-Regression Testing is different from Nonparametric Regression Testing?

Nonparametric regression is a type of regression analysis in which the predictor does not take a predetermined form but is built based on data information.

That is, no parametric form for the relationship between predictors and the dependent variable is assumed.

Nonparametric regression necessitates larger sample sizes than parametric regression because the data must supply both the model structure and the model estimates.

Non-Regression Testing Example

Non-regression testing can be incorporated into regression analysis. Here’s a rundown of how it works.

For example, assume there is an existing functionality A tested and a new functionality B that has just been added to the product.

So, for the time being, the program functionality is A+B. Non-regression testing will only cover functionality B. However, new functionality – C – will be added later. If we want regression testing, we’ll need to run the tests for A and B functionality. Non-regression tests are incorporated into regression testing.

Use of Non-Regression Testing

Non-regression testing is used when system components evolve, or new system components (and functionality) are added.

Its goal is to ensure that the changes are correct and that no regression bugs have appeared in the system due to the recent evolution.

In general, previous test sequences are launched to ensure that the system’s testing quality has not deteriorated.

The test plan specifies the components to be tested following the evolution or modification of a system component.

How To Automate Regression Testing?

Regression testing is a multi-layered process due to its extensive coverage and technical complexity. Here’s a step-by-step guide to regression testing and incorporating automation into the workflow.

At this stage, a developer estimates which system components will be changed and the extent of the change.

Impact analysis of software changes:

This stage entails outlining all of the possible consequences of the code change across the system, identifying all systems affected by a new fix or feature, estimating potential system damage and ways to deal with it.

It is creating a strategy for regression testing. The testing team outlines the workflow step by step at this stage. For example, a regression testing strategy might look something like this: 1) collect test data; 2) estimate execution time for test cases; 3) automate test cases; 4) execute tests; 5) report; and 6) iterate.

They are developing a test suite. At this point, a QA specialist creates automated tests.

Later, the regression when running automated tests on testing automation engineer writes scripts for execution in a scripted language selected by the team ahead of time.

Running regression tests When running automated tests, prioritize cases and evaluate test module reusability. Maintain a high frequency of testing and establish a flexible reporting system.

Reporting. At this point, QA specialists must explain the testing results to stakeholders such as a project manager, the end client, and anyone who is involved.

In addition, a developer must develop the metrics of analysis of the scope of testing and elaborate on how the testing session helped the team achieve a goal set during the planning stage to write a compelling summary report.


Non-regression testing entails simply testing. Regression testing entails repeatedly testing the application in two scenarios.

When a defect is discovered by a tester and corrected by a developer, the tester must focus on the defect functionality and related old functionality.

Once the changes have been incorporated into the application, the tester must test both the new and related old functionality to ensure that the related old functionality remains the same.

A tester always carries out Non-Regression Testing. If any defects are discovered, then you must perform Regression Testing.

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