Difference Between Retesting and Regression Testing with Example

Explanation on the Variance Between Retesting and Regression Testing:

Do you like delving into comparative articles? I unquestionably do. It is an exceptional method to prompt ideas, feedback, and even vigorous disputes.

The topic for discussion today is Retesting Vs Regression Testing.

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Let’s kick off with Retesting:

Retesting

Retest administrators carry out the same test once again, irrespective of the motive. Whenever a test is repeated, it falls under retesting. This could involve retesting the current version’s functionality, bug fixes, functionality from a prior version, or a test case that was just performed, etc.

Asking “why?” The following reasons are as good as any:

• If a defect was detected during a test conducted yesterday, and you want to validate the reproducibility of the defect and the steps, then retest is required.
• Upon completion of a test, if your focus was elsewhere (maybe you received a phone call, or were assisting a co-worker, etc.). You opt to retest for reassurance.

I hope this clarifies it.

Retesting is the repetition of a test for any reason, a term that holds true to its basic meaning.

Regression Test

Software progresses, newer versions are released on top of the old ones, introducing newer features and extensions over time. However, this may cause application instability.

Consider the analogy of building a block tower- placing one block on top of another. If you fail to strengthen or reinforce the base intermittently, the tower may collapse, right?

The same applies to software testing- you need to ensure your software’s base strength and stability.

By retesting the software, you can achieve this.

Suggested read => Defining Regression Testing? Tools and Suggested Approaches

Regression is a specialized form of Retest. The unique “Why” and “When” distinguish it from the latter.

1) When is retesting done? When modifications are made to the software

2) Why is retesting done? To ascertain that the new components/changes haven’t caused any instability in the previously functional functionalities. Regression is typically carried out in the following situations:

• Upon the release of a new version (Perform regression for all or at least the critical features of the older version)
• Upon a bug fix completion

It’s crucial to recognize that while exhaustive regression testing can’t usually be performed, it’s still desired.

It is advisable to conduct a Regression Analysis before diving into actual testing. This process involves deciding upon the extent of regression testing required for the application.

What influences the depth of the regression testing to be performed?

• The nature of modification
• The impact of the changes on the current system/feature
• The available resources and time

What can help testers determine the required depth of regression testing?

1) Familiarity with the application and accumulated experience

2) By conferring with the developers

3) The location of the change. For example, if the modification is on the homepage, it would demand more attention compared to one on a less frequented page.

The test team can select one among the following approaches based on the influencing factors:

• Unit Regression
• Partial Regression
• Complete Regression

Unit regression signifies retesting solely the modified part/section of the application.

Partial regression covers the retesting of the modified parts and the ones it interacts with.

Full regression entails testing the complete application, regardless of the modification’s location.

The strategy’s selection depends on factors like time & resource constraints, the significance of the changes (and their impacts), developers’ advice, etc. Opting for the right set of tests over testing everything boosts efficiency.

A comprehensive Regression Analysis is the keystone to success. This process necessitates smart work, not just strenuous efforts.

Dispelling the Myths about Regression Testing

Below are the clarifications of common misconceptions about Regression Testing:

#1) Regression is always automated: This is not entirely true. Manual regression testing is also valid. We have an entire piece written on this => How is Regression Testing Achieved? Is Manual Intervention Feasible?

But, regression is indeed an ideal candidate for automation. The time and monotony involved in repeated testing might lead to overlooking crucial validations. Automation serves as a reliable, swift, and efficient alternative.

Additional reading => Challenges Faced in Automated Regression Testing

#2) Regression is never complete: This isn’t completely accurate.

Exhaustive regression testing might not be feasible, but it isn’t always necessary.

For example, in case of a trivial typing error correction on the homepage, retesting the feature would be sufficient, and full-scale regression of the rest of the homepage functionality would be unnecessary.

#3) Time constraints render regression unnecessary: This isn’t accurate. Insufficient regression testing leads to product uncertainty. You won’t be aware of how the software would react under various user scenarios.

#4) Regression implies running every single preceding test case: Again, not correct. Instead of selecting every test case, strategic selection is more advisable. Comprehend the changes and choose the relevant test cases.

So we have covered both Retesting and Regression Test in detail.

Now, let’s draw a comparison.

Retesting Vs Regression Testing

How are they similar?

• Both necessitate repetition
• They use validation or black box testing techniques
• Both retest or regress test cases, either automated or manual
• They share the common goal to verify, clarify doubts and ensure certainty

How are they different?

• Retesting applies to any test – be it current or previous version functionality, whereas Regression focuses on previous version functionality.
• Retesting isn’t reliant on software changes, whereas Regression is.

In summary:

Consider a scenario where you have a test case XYZ, which led to a defect with ID 120. This defect is corrected in the next release. In response, you retest test case XYZ and perform regression on the related functionality. Regression testing helps ensure that all functionality is working as expected after the correction of defect 120. Retesting validates the resolution of the defect itself.

Hence, it’s evident that the real power lies not in the individual uses, but in the combined utilization of both Regression and Retesting.

Now, it’s your turn. Would you agree with the definitions and analysis provided in this article?

About the author: This article is penned by Swati S., a member of the STH team.

We would love to hear your thoughts, opinions, and queries on this discussion. Please feel free to share, and we hope to connect with you all.

=> Click Here to Access the Comprehensive Regression Testing Series.